[1-2-1] UK/US spelling issues

Quake uses UK spellings for consistency, except for console commands which remain in US spelling.

To ensure a uniform appearance, UK spellings are used for all words in the guide. This decision was made partly in response to feedback from British players and to simplify the spell-checking process. If this presents an issue for any user, please provide feedback as solutions can be arranged.

Note: All console commands will continue to use US spelling, for example, 'COLOR' and not 'COLOUR'.