Fix mutated line endings on Windows

It prevents Git from modifying files on checkout. By default, it
converts LF line-endings to CRLF on Windows which leads to inconsistency
and ESLint `linebreak-style` with `unix` (LF) value to fail.

It also solves failed builds in GitHub actions agents actions/checkout#135.

.eslintrc.js

@@ -52,7 +52,7 @@ function getOwnRules() {
   return {
     'no-console': process.env.NODE_ENV === 'production' ? 'warn' : 'off',
     'no-debugger': process.env.NODE_ENV === 'production' ? 'warn' : 'off',
-    'linebreak-style': ['error', 'unix'], // Also enforced in .editorconfig
+    'linebreak-style': ['error', 'unix'], // This is also enforced in .editorconfig and .gitattributes files
     'import/order': [ // Enforce strict import order taking account into aliases
       'error',
       {

.gitattributes

@@ -0,0 +1,6 @@
+# Prevent Git from auto-converting to CRLF on Windows, and convert to LF on checkin.
+#   *           : All files
+#   text=auto   : If Git decides content it text, it converts CRLF to LF on checkin.
+#   eol=lf      : forces Git to normalize line endings to LF on checkin and prevents conversion
+#                 to CRLF when the file is checked out.
+* text=auto eol=lf