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/is-fullwidth-code-point/index.d.ts

@@ -0,0 +1,17 @@
+/**
+Check if the character represented by a given [Unicode code point](https://en.wikipedia.org/wiki/Code_point) is [fullwidth](https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms).
+
+@param codePoint - The [code point](https://en.wikipedia.org/wiki/Code_point) of a character.
+
+@example
+```
+import isFullwidthCodePoint from 'is-fullwidth-code-point';
+
+isFullwidthCodePoint('谢'.codePointAt(0));
+//=> true
+
+isFullwidthCodePoint('a'.codePointAt(0));
+//=> false
+```
+*/
+export default function isFullwidthCodePoint(codePoint: number): boolean;