Support for aligning with declaration words (let,var,const,etc.)

[sylido]

This seems to solve the main problem I was having with this package for a while, being able to select all my vars and use the alignment to auto-align.

The declaration words are customizable through the new declarations field in the settings file, by default those are the "var", "let", "const" ones.

Added : to the list of defailt alignment characters as it is very useful for json formatting. The : will now also get an empty space in front and behind it as well.

Can format a whole file correctly as well, but it's buggy with longer files. Just have to not select anything in the file to trigger that with the same shortcut.

Includes fixes from some other PRs in the hope of getting this reviewed and merged in.

Have tested it for a year+ without having any issues with my usual workflow.