Tests: Add tests and improve coverage

[anirudhsudhir]

• Write tests for various components of the ssg

  • tests for helper package
  • tests for engine package
  • tests for parser package
  • tests for the zettel feature
  • benchmark for main.go

• Add status checks for PRs and fix netlify deploy preview

• Minimum test coverage of 50% for all packages

  • Improve engine/ test coverage

[bwaklog]

• Reached 71.2% coverage with engine package : perf:154405e
• Added tests for engine pacakge

[anirudhsudhir]

• Remove generated test output files and ignore the directories in .gitignore
• Add a cleanup script to delete test output
• Switch to the deep data merge implementation and update tests

[anirudhsudhir]

• Add tests got helper/ and notes/
• coverage of >50% for all packages under pkg/