Add altClickForMouseEvents option for issue #5952

When enabled during mouse events mode, click/drag/move events require the alt
key while wheel events are unaffected. Selection stays enabled by default
and takes precedence over macOptionClickForcesSelection.

Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>

src/common/services/OptionsService.ts

@@ -52,6 +52,7 @@ export const DEFAULT_OPTIONS: Readonly<Required<ITerminalOptions>> = {
   windowOptions: {},
   windowsPty: {},
   wordSeparator: ' ()[]{}\',"`',
+  altClickForMouseEvents: false,
   altClickMovesCursor: true,
   convertEol: false,
   termName: 'xterm',