[spacemacs-layouts] add details of restricted functions

[practicalli-johnny]

Detail how to use the layer variables to make use of restricted functions and
limit their scope to within a layout.

Documentation copied from the following commit, which did not get included along with the code
https://github.com/syl20bnr/spacemacs/tree/0e9866efcee9915f3418cec11371d02ee619ced2/layers/%2Bspacemacs/spacemacs-layouts

[practicalli-johnny]

I initially forgot to add an entry in the CHANGELOG,develop. This has now been squashed and pushed.
I also found a rogue character that had sneaked into the README.org file, so deleted that and pushed.

[duianto]

Thank you for contributing to Spacemacs. It's safe to delete your branch.
The changes have been applied to the develop branch.
Commit(s): b0d1585

[duianto]

I forgot that magit strips brackets from the commit name by default, when applying a patch.

I've saved C-x C-s the Apply patches w setting:
-b Limit removal of email cruft (--keep-non-patch)
before, but I must have reinstalled since then. My bad.

[practicalli-johnny]

Looking at the Spacemacs commit history, it seems most of the commits do not have the layer name in Square brackets. I didn't realise it maybe because of magit. Will have to look up that feature.

Thanks for your help.

[duianto]

They aren't required, but it's probably helpful when there are leading brackets in the commit subject, with the layer or section (ex: [docs]). Then it's easy to see which sections the commit targets.

You did everything right, It was my mistake for not remembering to turn off the bracket removal after reinstalling Spacemacs. I wrote it down and hopefully I'll remember to check the notes during the next reinstall.

Thanks again for improving the documentation.