Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/update-browserslist-db/utils.js

@@ -0,0 +1,25 @@
+const { EOL } = require('os')
+
+const getFirstRegexpMatchOrDefault = (text, regexp, defaultValue) => {
+  regexp.lastIndex = 0 // https://stackoverflow.com/a/11477448/4536543
+  let match = regexp.exec(text)
+  if (match !== null) {
+    return match[1]
+  } else {
+    return defaultValue
+  }
+}
+
+const DEFAULT_INDENT = '  '
+const INDENT_REGEXP = /^([ \t]+)[^\s]/m
+
+module.exports.detectIndent = text =>
+  getFirstRegexpMatchOrDefault(text, INDENT_REGEXP, DEFAULT_INDENT)
+module.exports.DEFAULT_INDENT = DEFAULT_INDENT
+
+const DEFAULT_EOL = EOL
+const EOL_REGEXP = /(\r\n|\n|\r)/g
+
+module.exports.detectEOL = text =>
+  getFirstRegexpMatchOrDefault(text, EOL_REGEXP, DEFAULT_EOL)
+module.exports.DEFAULT_EOL = DEFAULT_EOL