fix: remove internal types on publish

[styfle]

Fixes consumers using TS failing with

Error: ../../node_modules/@vercel/nft/out/types.d.ts(3,34): error TS2307: Cannot find module 'estree' or its corresponding type declarations.
Error: Command failed: tsc

This moves internal types to ./utils/types.ts and deletes those upon publishing.

The external types will continue to live in ./types.ts.

[codecov]

Codecov Report

Merging #223 (5c5b173) into main (47f890a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #223   +/-   ##
=======================================
  Coverage   80.04%   80.04%           
=======================================
  Files          13       13           
  Lines        1433     1433           
  Branches      537      537           
=======================================
  Hits         1147     1147           
  Misses        114      114           
  Partials      172      172           

Impacted Files	Coverage Δ
src/analyze.ts	86.57% <ø> (ø)
src/utils/special-cases.ts	88.60% <ø> (ø)
src/utils/static-eval.ts	82.95% <ø> (ø)
src/utils/wrappers.ts	74.75% <ø> (ø)

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