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/v8-to-istanbul/lib/function.js

@@ -0,0 +1,29 @@
+module.exports = class CovFunction {
+  constructor (name, startLine, startCol, endLine, endCol, count) {
+    this.name = name
+    this.startLine = startLine
+    this.startCol = startCol
+    this.endLine = endLine
+    this.endCol = endCol
+    this.count = count
+  }
+
+  toIstanbul () {
+    const loc = {
+      start: {
+        line: this.startLine,
+        column: this.startCol
+      },
+      end: {
+        line: this.endLine,
+        column: this.endCol
+      }
+    }
+    return {
+      name: this.name,
+      decl: loc,
+      loc: loc,
+      line: this.startLine
+    }
+  }
+}