20240826 subfolder merge strategies

[stefan-b-jakobsson]

This PR is just testing subfolder merge strategies. Here adding the bootloader project as a subfolder. I think it looks pretty clean.

Git commands used to produce the local repo:

git clone https://github.com/X16Community/x16-smc.git
cd x16-smc
git remote add -f bootloader https://github.com/stefan-b-jakobsson/x16-smc-bootloader.git
git merge -s ours --allow-unrelated-histories --no-commit bootloader/20240711-v3   
git read-tree --prefix=bootloader/ -u bootloader/20240711-v3
git commit -m "Merge bootloader project"    

[stople]

Not sure if it becomes more or less clean, but, one option can be to add one commit to your source repo/source branch where you move all files in the repo to the appropriate sub folder. Then, the merge commit will just merge these commits without "altering" (moving) files as well. (After merge, your private repo should preferably be abandoned). Except this suggestion, it seems like you were able to properly merge the repos.