fix: throw error when typescript is missing

[jordanshatford]

closes: #365

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🦋 Changeset detected

Latest commit: c85a324

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@hey-api/openapi-ts	Patch

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 84.12%. Comparing base (974dd72) to head (c85a324).

Files	Patch %	Lines
packages/openapi-ts/src/index.ts	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #366      +/-   ##
==========================================
- Coverage   84.15%   84.12%   -0.03%     
==========================================
  Files          73       73              
  Lines        4809     4813       +4     
  Branches      547      548       +1     
==========================================
+ Hits         4047     4049       +2     
- Misses        761      763       +2     
  Partials        1        1              

Flag	Coverage Δ
unittests	84.12% <50.00%> (-0.03%)	⬇️

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