docs: migrate external tilest info (#3249)

data/json/external_tileset/README.md

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+../../../doc/src/content/docs/en/mod/json/reference/graphics/external_tileset.md

doc/src/content/docs/en/mod/json/reference/graphics/external_tileset.md

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+---
+title: External Tilesets
+---
+
+`data/json/external_tileset` is used for content specific to Bright Nights which are not presently
+in primary tilesets such as UDP or Ultica, for which `looks_like` is inadequate to depict the
+content to a satisfactory degree. It functions using the `mod_tileset` feature, applying any desired
+new sprites or overriding sprites to the specified tileset.
+
+The primary advantage of this method is to set aside sprites so they won't interfere with updating
+the tilesets themselves (as their sources are in the repositories of the tileset authors), and
+likewise ensuring anything specific to BN won't be accidentally erased, like it would if a tileset
+update was submitted to BN after these editing these sprites our versions of the tilesets. It also
+covers divergences in content were, by nessecity, a different sprite is a better fit.
+
+Links to relevant pull requests, for content covered below:
+
+- Steam turbine: [#2815](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2815)
+- Bullet animations: [#1861](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/1681)
+- Wooden shields, riot shields, and ballistic shields:
+  [#2851](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2851)
+- Lead sling bullet: [#2709](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2709)
+- Leather and banded shields: [#2856](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2856)
+- Edits to blueberry bushes, strawberry bushes, and cherry trees:
+  [#2861](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2861)
+- De-obsoleted wooden greatbow, reflavored compound/composite greatbow:
+  [#2862](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2862)
+- Katar and sai: [#2715](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2715)
+- Utility light can be switched off:
+  [#1003](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/1003)
+- Mi-go nerve cluster: [#1962](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/1962)
+- Scaled bear: [#1371](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/1371)
+- Buckler and welded shield: [#2878](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/2878)
+- Battle masks and bronze arm guards:
+  [#3221](https://github.com/cataclysmbnteam/Cataclysm-BN/pull/3221)
+
+## Undead People
+
+The following is a current list of sprites this folder adds to the UDP tileset, in which files and
+for what purpose. This is currently the only tileset with external_tileset coverage, but sprites for
+Ultica are planned for the future.
+
+### External_Tileset_DP_Normal.png
+
+- Furniture form of steam turbines, to be deconstructed for advanced steam engine. Content specific
+  to BN.
+- Animation effects for bullets in flight. Feature specific to BN.
+- Wooden shield, including worn and wielded. Item specific to BN.
+- Riot shield, including worn and wielded. Item specific to BN.
+- Ballistic shield, including worn and wielded. Item specific to BN.
+- Lead sling bullet. Item specific to BN, `looks_like` of `rock` did not seem fitting
+- Leather-reinforced shield, including worn and wielded. Item specific to BN.
+- Large leather-reinforced shield, including worn and wielded. Item specific to BN.
+- Banded shield, including worn and wielded. Item specific to BN.
+- Large banded shield, including worn and wielded. Item specific to BN.
+- Swapped spring and summer sprites (the latter not depicting young berries) for blueberry bush, as
+  harvest season has been moved in BN.
+- Swapped spring and summer sprites (the latter not depicting young berries) for strawberry bush, as
+  harvest season has been moved in BN.
+- Fixed worn sprite for `woodgreatbow`, as it had a sprite error in its UDP version.
+  `Note: this can be removed once UDP is updated in BN, as the fix has been published in the source repository.`
+- Overriding sprite for `compgreatbow`, as its version in BN is modeled after a composite bow
+  instead of a compound bow.
+- New worn sprite for `compgreatbow`, as compound greatbow in DDA can't be worn thus UDP lacks a
+  worn sprite for it (which we'd liklely need to edit to resemble composite bow anyway).
+- Katar, including sprite for wielded state. Item specific to BN.
+- Sai (weapon, not to be confused with telecoms location), including sprite for wielded state. Item
+  specific to BN.
+- Welded shield, including worn and wielded. Item specific to BN.
+- Buckler, including worn and wielded. Item specific to BN.
+- Battle masks, iron and bronze, including worn sprites. Items specific to BN.
+- Bronze arm guards, including worn sprites. Item specific to BN.
+
+### External_Tileset_DP_Large.png
+
+- Off state for utility light. Ability to switch on and off specific to BN.
+- Alien nerve cluster, furniture added to mi-go locations in BN.
+  `Note: this can be removed once UDP is updated in BN, as the sprite for this has been published in the source repository.`
+- Scaled bear, including corpse. Monster specific to BN.
+- Cherry tree uses summer sprite (plus cherry blossom coloration), summer sprite depicted without
+  berries, due to harvest season being moved in BN.