Add Standalone Script Compiler Build configuration

[drojf]

Note: this PR was written ontop of the other window resolution fixes PR here: #128 . That other PR should be merged first.

This PR adds an additional build configuration which produces a standalone "Script Compiler" executable (without Unity).

This avoids needing to run a skeleton of the game just for the purpose of building the game scripts (note: currently script compilation on Github Actions is not working for all chapters)

The PR is in Draft because I still need to:

• Merge other PR Mod Resolution and Windowed/Fullscreen mode fixes #128
• Tidy up this PRs commit history
• Test in github actions
• Verify compiled scripts are identical to ones generated by the game
• See if there will be any problems merging this with later chapters as the .csproj is slightly different on later chapters
• Merge this into every chapter