feat: adds support for Data API in Github#getFileContents

[lancedikson]

It brings a unified function for getting file contents with or without Data API.

Fixes #546 🦕

[codecov]

Codecov Report

Merging #551 into master will increase coverage by 0.16%.
The diff coverage is 98.43%.

@@            Coverage Diff             @@
##           master     #551      +/-   ##
==========================================
+ Coverage   82.35%   82.51%   +0.16%     
==========================================
  Files          42       42              
  Lines        4856     4907      +51     
  Branches      394      433      +39     
==========================================
+ Hits         3999     4049      +50     
- Misses        856      857       +1     
  Partials        1        1              

Impacted Files	Coverage Δ
src/github.ts	81.03% <98.43%> (+1.01%)	⬆️

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[bcoe]

I love how you've approached this as a progressive enhancement 👍

I'll get this shipped this morning and comment back on the issue, so that you can test things out.

[lancedikson]

Great, thanks, @bcoe, for the feedback and such a quick merge! Appreciate it! 👍 Strange that this issue didn't pop up before as we noticed it just a couple of weeks after we started using release-please. It would be great if you could also publish a new version of release-please-action as we rely on that as a final product :) Thanks again, and have a great weekend!