* neomutt: support list in binds.map
Closes#1245
Adds support for specifying programs.neomutt.binds[].map as a list. If
specified as a list, then the binds will be concatenated with a ",".
* neomutt: add deprecation warning for (binds|macros).map as string
Added note that specifying 'programs.neomutt.(binds|macros).map' as a string is deprecated. Instead, use the list form.
* neomutt: note deprecation warning in release notes
Added note that specifying 'programs.neomutt.(binds|macros).map' as a
single string is deprecated in favor of specifying it as a list
* neomutt: add assertion that map is not empty
Added an assertion that each 'programs.neomutt.(binds|macros).map' list contains at least one element.
