dotnet build does not need to run when merging to main #120

The full build process does not need to run on PRs / merges that occur into the main branch.

Feature work occurs in feature branches, which should still get builds so as to check that they can successfully build upon each commit.
However, merges into main are generally just for syncing releases and placing the latest changes into the main branch. So, the build process does not need to run for these commits as the build and release process will already be completed.