Merge branch 'eslint-check-file-names' into 'master'

Check that JavaScript file names match convention

## What does this MR do?

Introduce a new ESLint rule to check JavaScript file names.

## What are the relevant issue numbers?

fixes #23118

See merge request !7238

.eslintrc

 {
   "extends": "airbnb",
+  "plugins": [
+    "filenames"
+  ],
+  "rules": {
+    "filenames/match-regex": [2, "^[a-z_]+$"]
+  },
   "globals": {
     "$": false,
     "_": false,

CHANGELOG.md

@@ -27,6 +27,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 - Removed delete branch tooltip !6954
 - Stop unauthorized users dragging on milestone page (blackst0ne)
 - Restore issue boards welcome message when a project is created !6899
+- Check that JavaScript file names match convention !7238 (winniehell)
 - Do not show tooltip for active element !7105 (winniehell)
 - Escape ref and path for relative links !6050 (winniehell)
 - Fixed link typo on /help/ui to Alerts section. !6915 (Sam Rose)

package.json

@@ -7,6 +7,7 @@
   "devDependencies": {
     "eslint": "^3.1.1",
     "eslint-config-airbnb": "^12.0.0",
+    "eslint-plugin-filenames": "^1.1.0",
     "eslint-plugin-import": "^2.0.1",
     "eslint-plugin-jsx-a11y": "^2.2.3",
     "eslint-plugin-react": "^6.4.1"