feat(resolve-url): convert package to TypeScript

[jordan-a-young]

Summary

Converts the @availity/resolve-url package from JavaScript to TypeScript.

Changes

• Renamed all .js source files to .ts and added explicit types
• Removed hand-written .d.ts declaration files (now generated by tsup)
• Updated package.json build scripts to reference src/index.ts
• Added string[][] type annotation to segmentBuffers to resolve inference issues
• Replaced non-null assertions with a typed lastOf helper for safe array access
• Replaced deprecated substr with slice throughout
• Replaced indexOf() === 0 checks with startsWith()
• Removed redundant JSDoc type annotations (types now live in signatures)
• Added JSDoc comments to isAbsoluteUrl and resolveUrl
• Added missing test cases for isAbsoluteUrl TypeError guard and resolveUrl base parameter
• Fixed window.location.href → window.location.origin in Docusaurus docs
• Updated apps.availity.com → essentials.availity.com in README and JSDoc examples

Testing

• 127 tests passing (up from 122 before added coverage)
• Lint clean
• TypeScript typecheck clean