Block reactions on locked issues

[j-f1]

Currently, attempting to add a reaction to a locked issue or one of its comments causes an error: “username does not have the correct permissions to execute `AddReaction`.” This occurs even if you have write access to the repository.

To prevent the error from popping up, the 😃➕ button should be hidden, double-taps should do nothing, and tapping on the reaction emoji should do nothing if the issue is locked.

Bug Report Dump (Auto-generated)

Version 1.23.0 (1539487256)
Device: iPhone 8 (iOS 12.0)
TestFlight: true

[j-f1]

@vvolodin why the 👎?