Feature (low priority): In file diff panels, support double clicking a word and highlight its occurences

[sken130]

By default, SourceGit should know a lot of file extensions' defaults, for example:

Case sensitive: .py, .cs, .java, .js, .jsx .ts, .tsx, .rs
Case insensitive: .vb, .sql
Harder ones: .html (case insensitive, but embedded JavaScripts are case sensitive)

Allow user to specify the case sensitivity for other file extensions

Have global config to specify the default case sensitivity for non recognized file extensions

Should match whole word