Add Loader support for quilt.mod.json5

[EnnuiL]

Creating this PR as a draft until support on Quilt Loom's side is worked on, but so far? I believe the Loader-side support is solid! Reviews are appreciated

The benefits of JSON5 will be great for developers

[EnnuiL]

Work on Quilt Loom has been pushed as quilt-loom#36!

[EnnuiL]

As a note, I've noticed that Quilt Parsers hasn't been relocated properly; I went ahead and fixed that

[EnnuiL]

I went ahead and expanded the QMJ5 handling by having the Loader error out if a QMJ is also found, which prevents from further deviation from its intended purpose;
The funny thing was that with that, I managed to catch an issue where mods with duplicate metadata were being iterated through twice! And this extended to mods containing both a QMJ and a FMJ! I do wonder if it could be done in a more effective way though;
anyway, here's the screenshot!

[EnnuiL]

In order to prevent trouble (although with some trouble being caused as a side-effect), I've made the QMJ5 support opt-in, so the build system has to explicitly ask for it in order for things to work;
This may make migrating from a QMJ workspace to a QMJ5 one more difficult though, so I'll have to tackle that issue myself somehow

[EnnuiL]

Update: by using the Fabric DLI system, a migration from an already-existing QMJ workspace to a QMJ5 one should be smooth

[EnnuiL]

Update: by using the Fabric DLI system, a migration from an already-existing QMJ workspace to a QMJ5 one should be smooth

Tackled by quilt-loom#37

[EnnuiL]

oh boy, here we go;
Rebased to QLoader 0.26.4, see quilt-loom#53 for new companion PR

[AlexIIL]

I'm sorry for taking this long - and thanks for updating this!