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/html-entities/dist/esm/surrogate-pairs.js

@@ -0,0 +1,15 @@
+export var fromCodePoint = String.fromCodePoint ||
+    function (astralCodePoint) {
+        return String.fromCharCode(Math.floor((astralCodePoint - 0x10000) / 0x400) + 0xd800, ((astralCodePoint - 0x10000) % 0x400) + 0xdc00);
+    };
+// @ts-expect-error - String.prototype.codePointAt might not exist in older node versions
+export var getCodePoint = String.prototype.codePointAt
+    ? function (input, position) {
+        return input.codePointAt(position);
+    }
+    : function (input, position) {
+        return (input.charCodeAt(position) - 0xd800) * 0x400 + input.charCodeAt(position + 1) - 0xdc00 + 0x10000;
+    };
+export var highSurrogateFrom = 0xd800;
+export var highSurrogateTo = 0xdbff;
+//# sourceMappingURL=surrogate-pairs.js.map