chore: remove legacy build tooling

Drops api-extractor.json, .svgrrc.js, and .npmignore. The new build
pipeline (tsup + npm "files" field) replaces all three:

- api-extractor was used to roll up .d.ts files; tsup emits declarations
  directly per entry.
- SVGR is no longer used to convert icons; a small Node script reads
  feather-icons' contents and emits TSX via a shared factory instead.
- .npmignore is redundant once package.json declares an explicit
  "files" allowlist.

Author: yigithanyucedag