Housekeeping (#2520)

* enhance(project): Add .prettierrc to project
* chore(deps): Bump dependencies
* chore(view): Improve readability of the search form view
* chore(admin): Improve language used in the customize_register filter docblock
* chore(lint): Lint project assets
* chore(change-log): Improve/prepare the changelog for actual release
* chore(readme): Improve README feature list
* chore(readme): Update README theme directory structure
* chore(readme): Add GitHub sponsors badge
* chore(readme): Clean up various wording
* fix(ci): Fix failing tests
* fix(mix): Add index.php to purgecss scope (Supersedes #2423) (Credit @oxyc)

composer.json

@@ -40,7 +40,7 @@
   },
   "require": {
     "php": "^7.2.5",
-    "roots/acorn": "^1.0.1"
+    "roots/acorn": "^1.1"
   },
   "require-dev": {
     "filp/whoops": "^2.7",