Add instructions for people with domains that do not support custom addins

[rubenhensen]

Some outlook domains do not allow for custom add ins. The custom add ins menu just is not there for those users, making it confusing to people trying to follow the instructions.

[rubenhensen]

/dobby fix this issue, there are other dobbies also working, so make sure the PR has not conflicts

[dobby-coder]

🪄 Dobby is on it! Dobby will look into adding instructions for users whose Outlook domain does not allow custom add-ins. Dobby will check in with other dobbies to avoid conflicts!

[dobby-coder]

Opened #199 with a fix: a callout above the Outlook install instructions warning users whose accounts don't allow custom add-ins, before they download the manifest and get stuck. Conflict-avoidance: the change adds a new addons.outlookWarning i18n key on its own lines instead of editing the existing addons.Outlook string, so it doesn't collide with the other in-flight Outlook PRs (#189, #190, #191, #193, #195, #196). CI green, ready for review.

[dobby-coder]

Already shipped via #204 (merged 2026-05-08). Verified the relevant fix is on main. Safe to close.

[dobby-coder]

Resolved by #204 (consolidated addon install-doc, i18n & UI fixes). The original sub-PR for this issue was rolled into that consolidation, but the closing keyword didn't propagate, so closing manually.