fix: trim empty lines

[mmkal]

this prevents an interaction with other lint rules which expect newlines at the end of the file

[github-actions]

@mmkal - changes were pushed to your branch: 7a9d9e8.

[codecov-io]

Codecov Report

Merging #201 into main will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #201   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           40        40           
  Lines          710       710           
  Branches       115       116    +1     
=========================================
  Hits           710       710           

Impacted Files	Coverage Δ
packages/eslint-plugin-codegen/src/index.ts	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e5d9bc3...1fc4d89. Read the comment docs.