Add eslint, stylelint, prettier, and pre-commit (#484)

- When you try to commit, Pre-commit will run checks for all three, if
  installed, _only_ on staged files, and prevent committing if the linters are
  unhappy.
- Several eslint rules that generate a lot of errors are disabled for now.
  That's to allow a more gradual transition, so you won't change 1 line and be
  told to fix 100 other lines (but maybe like 20 because there are still a lot
  of rules enabled).
- Prettier is set to require pragma. That's also to allow a more gradual
  transition. As each file is tidied up, run Prettier on it, and it'll add a
  special comment that tells it that it's now responsible for keeping that one
  tidy.

.pre-commit-config.yaml

@@ -0,0 +1,28 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: "v2.2.1"
+    hooks:
+      - id: prettier
+        files: "assets/js|assets/css"
+        args: [--config, assets/.prettierrc.json]
+  - repo: https://github.com/awebdeveloper/pre-commit-stylelint
+    rev: 'f792d6b'
+    hooks:
+    -   id: stylelint
+        additional_dependencies:
+          - stylelint@13.2.1
+          - stylelint-config-standard@20.0.0
+  - repo: https://github.com/pre-commit/mirrors-eslint
+    rev: 'v7.15.0'
+    hooks:
+      - id: eslint
+        files: "assets/js"
+        additional_dependencies:
+          - eslint@7.2.0
+          - eslint-config-airbnb@18.2.0
+          - eslint-plugin-import@2.22.1
+          - eslint-plugin-jsx-a11y@6.4.1
+          - eslint-plugin-react@7.21.5
+          - eslint-plugin-react-hooks@4.2.0

assets/.eslintrc.json

@@ -0,0 +1,14 @@
+{
+  "extends": ["airbnb", "prettier"],
+  "plugins": ["prettier"],
+  "rules": {
+    "max-len": [2, {"code": 100}],
+    "prettier/prettier": [2],
+    "react/jsx-filename-extension": [1, { "extensions": [".js", ".jsx"] }],
+    "react/destructuring-assignment": [0],
+    "react/prop-types": [0],
+    "max-classes-per-file": [0],
+    "react/jsx-one-expression-per-line": [0],
+    "react/self-closing-comp": [0]
+  }
+}

assets/.prettierrc.json

@@ -0,0 +1,5 @@
+{
+  "singleQuote": true,
+  "requirePragma": true,
+  "insertPragma": true
+}

assets/.stylelintrc.json

@@ -0,0 +1,22 @@
+{
+  "extends": [
+    "stylelint-config-standard",
+    "stylelint-config-prettier"
+  ],
+  "rules": {
+    "at-rule-no-unknown": [
+      true,
+      {
+        "ignoreAtRules": [
+          "tailwind",
+          "apply",
+          "variants",
+          "responsive",
+          "screen"
+        ]
+      }
+    ],
+    "declaration-block-trailing-semicolon": null,
+    "no-descending-specificity": null
+  }
+}

assets/package.json

@@ -37,5 +37,18 @@
     "url-search-params-polyfill": "^8.0.0",
     "webpack": "4.39.2",
     "webpack-cli": "^3.3.12"
+  },
+  "devDependencies": {
+    "eslint": "^7.2.0",
+    "eslint-config-airbnb": "^18.2.0",
+    "eslint-config-prettier": "^7.0.0",
+    "eslint-plugin-import": "^2.22.1",
+    "eslint-plugin-jsx-a11y": "^6.4.1",
+    "eslint-plugin-prettier": "^3.3.0",
+    "eslint-plugin-react": "^7.21.5",
+    "eslint-plugin-react-hooks": "^4.2.0",
+    "stylelint": "^13.8.0",
+    "stylelint-config-prettier": "^8.0.2",
+    "stylelint-config-standard": "^20.0.0"
   }
 }