Shove the whole codebase through Prettier

[dtinth]

This PR makes Bemuse use Prettier’s code formatting style instead of using Standard. Other Standard rules (that has to do with common errors) stay intact though, but stylistic issues are now governed by Prettier.

Rationale:

• Recently there are weird cases when prettier-eslint sometimes fail on ESLint step, and causes the source file to be formatted using only Prettier. Rather than fiddling with these tools to get the code to be compliant with Standard, I decided to use only Prettier to handle stylistic issue now.

• Prettier supports more languages and results in more consistent formatting. (YAML, JSON, and SCSS files are now formatted using Prettier in this PR.)

Tasks:

• Set up Prettier

• Remove prettier-eslint

• Update docs

• Bring back style checking into Danger

[codecov-io]

Codecov Report

Merging #513 into master will decrease coverage by 0.02%.
The diff coverage is 89.66%.

@@            Coverage Diff             @@
##           master     #513      +/-   ##
==========================================
- Coverage   83.55%   83.52%   -0.03%     
==========================================
  Files         171      171              
  Lines        5400     5403       +3     
  Branches        1        1              
==========================================
+ Hits         4512     4513       +1     
- Misses        888      890       +2

Impacted Files	Coverage Δ
src/app/interactors/getLR2Score.js	100% <ø> (ø)	⬆️
src/game/input/control.js	100% <ø> (ø)	⬆️
src/bootstrap/index.js	75% <ø> (ø)	⬆️
src/app/entities/Options.spec.js	100% <ø> (ø)	⬆️
packages/bemuse-notechart/src/data/GameNote.js	100% <ø> (ø)	⬆️
src/app/entities/Collections.spec.js	100% <ø> (ø)	⬆️
packages/bms/src/speedcore/segment.js	100% <ø> (ø)	⬆️
src/game/test-helpers/index.js	100% <ø> (ø)	⬆️
src/app/song-loader/song-loader.worker.js	100% <ø> (ø)	⬆️
packages/bemuse-notechart/src/data/GameEvent.js	100% <ø> (ø)	⬆️
... and 95 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update cf2bd47...f316548. Read the comment docs.

[akibot]

	Fails
🚫	/home/circleci/bemuse/config/buildConfig.js line 14 – Read-only global 'name' should not be modified. (no-global-assign)
🚫	/home/circleci/bemuse/config/buildConfig.js line 21 – Read-only global 'name' should not be modified. (no-global-assign)
🚫	/home/circleci/bemuse/config/buildConfig.js line 24 – Read-only global 'name' should not be modified. (no-global-assign)
🚫	/home/circleci/bemuse/packages/bemuse-tools/src/server.js line 6 – Unable to resolve path to module 'rx'. (import/no-unresolved)
🚫	/home/circleci/bemuse/packages/bms/features/step_definitions/spacing_steps.js line 4 – Unnecessary escape character: -. (no-useless-escape)
🚫	/home/circleci/bemuse/packages/bms/features/step_definitions/spacing_steps.js line 4 – Unnecessary escape character: .. (no-useless-escape)
🚫	/home/circleci/bemuse/packages/bms/features/step_definitions/spacing_steps.js line 4 – Unnecessary escape character: -. (no-useless-escape)
🚫	/home/circleci/bemuse/packages/bms/features/step_definitions/spacing_steps.js line 4 – Unnecessary escape character: .. (no-useless-escape)
🚫	/home/circleci/bemuse/src/app/ui/ChangelogPanel.jsx line 3 – '$' is defined but never used. (no-unused-vars)
🚫	/home/circleci/bemuse/src/app/ui/ChangelogPanel.jsx line 4 – '_' is defined but never used. (no-unused-vars)

Generated by 🚫 dangerJS

[dtinth]

[ESLint issue will be fixed in a separate PR...]