Documentation Build Improvements

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Task description

Broken out from feedback on #961:

- Each build adds blank lines to the end of some files; ideally this would be idempotent and would not result in pending git changes.
- Investigate if we can read the target frameworks for each subsite from a common JSON location, or worst case set it in the powershell script

Locate the PowerShell build script and the generated documentation files or subsite configuration it uses. First reproduce a build and check for trailing blank-line changes, then inspect how target frameworks are currently supplied. Done means repeated builds are idempotent and framework targets come from a common JSON location or the script as described.

Written by the indexing model from the issue text.