docs(build): clarify dist/ vs root source files

[usernane]

Problem

• /AJAXRequest.js is 78KB
• /dist/AJAXRequest.js is 64KB

Unclear which is the canonical source and why they differ.

Suggestion

1. Document the build process in README or CONTRIBUTING.md
2. Add build script to package.json
3. Clarify in README which file to use for development vs production
4. Consider making /dist the only distribution folder

Proposed package.json scripts

{
  "scripts": {
    "build": "...",
    "minify": "terser AJAXRequest.js -o dist/AJAXRequest.min.js"
  }
}