Add signal for when contents of cell are changed

[iatenine]

Enhancement suggested by issue #11855. Creates a new signal for GridMap of "cell_contents_changed"
This signal passes info on the location of the cell updated as a Vector3

[aaronfranke]

@iatenine Is this still desired? If so, it needs to be rebased on the latest master branch. While there are no conflicts, rebasing is important so that reviewers can easily test the PR.

[iatenine]

@iatenine Is this still desired? If so, it needs to be rebased on the latest master branch. While there are no conflicts, rebasing is important so that reviewers can easily test the PR.

I don't understand. I only see the single "default" master branch and some version numbers. Is the master branch I'm trying to push to incorrect?

[aaronfranke]

The branch you have selected is correct, "master" is indeed what you want.

This PR is based on top of the master branch from 6 months ago, so if anyone compiles your branch then they are compiling Godot from 6 months ago. This is why it's often good to periodically rebase. Rebasing is required if there are conflicts, but your PR has none, so rebasing is optional but still nice to do. If you don't want to, you don't have to, it's just something to make maintainers' jobs easier, since then building your branch would build a more recent version of Godot.

It's also simply good to get a reply from you so that we can see you're still active and interested in this feature.

EDIT: Actually, you have two commits in this PR, so this would need a squash for it to be accepted.

[iatenine]

Not sure if I was meant to create a new PR effectively but have rebased and commited here #40044 and will be therefore closing this PR