Enable i18n for pages

• syntax, themes: update-kate-editor-org.pl script (frameworks/syntax-highlighting!564 (merged)) now generates only data files, custom_generation.py generates translation tables for syntax categories, syntax names, and theme names, the data and these translations are combined in the layout files
• the-team: the-team-update.pl script now generates only the team data file which is then used in the layout
• categories, tags: localize the titles
• non-auto-generated pages: build-it, join-us, kate-vi-mode, support

Pages that are still not localized:

• /post and its children
• /merge-requests and its children

README is updated.

BUG 468387