Fix Single new project

[hipstersmoothie]

What Changed

If last release is a commit sha, calc bump using SHA and bump current calculated version (most likely from package.json).

Why

When in a new project with no releases but with a version in package.json

1. Get latest release, it's a SHA
2. getCurrentVersion defaults to package.json version when it doesn't find a suitable tag
3. the currentVersion (unpublished) made it way to changelog creation. Where it uses the last release as the from in auto changelog
4. Since that version only exists in the package.json, git log creation would fail

now we check if the last release looks like a version number, and if it doesn't use the first commit to calculate a version bump and then bump the currentVersion with it.

Todo:

• Add tests
• Add docs
• Add SemVer label

[codecov]

Codecov Report

Merging #45 into master will increase coverage by 0.13%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #45      +/-   ##
==========================================
+ Coverage   76.23%   76.36%   +0.13%     
==========================================
  Files          13       13              
  Lines         871      876       +5     
  Branches      105      106       +1     
==========================================
+ Hits          664      669       +5     
  Misses        188      188              
  Partials       19       19

Impacted Files	Coverage Δ
src/github-release.ts	94.83% <100%> (+0.17%)	⬆️
src/main.ts	24.1% <100%> (ø)	⬆️

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