add open as encoding menu

[MisterChangRay]

Feature_Name

open jar file, some file need to edit; like:

but only ascii file can be directy edit, gbk or anther encoding showing like below:

hope add encoding menu to this

[Col-E]

Probably would better be implemented as a config value rather than cluttering the "open as" menu.

[Amejonah1200]

I propose of also adding a possibility for changing the encoding in an IntelliJ-like bottom bar. We could also add line breaks, and stats.