Remove logic constructing a11y announcements from reader.ftl.
Instead, reader will fetch and put together components as needed on the fly.
Follow-up to cde21ac9f2
per https://github.com/zotero/zotero/pull/4752#discussion_r1800481917
Also, add { general-key-command } and { general-key-alt } and add a reader
string that uses those on macOS and non-macOS for textual annotation
instructions. On macOS, the end of highlight and underline annotations is
resized via Shift+Command+arrows, which is different from the Option
modifier used in all other instances
(per https://github.com/zotero/reader/pull/138#issuecomment-2373775068)
Finally, tweak aria-description of "Find in Document" as it sounded
as if Control+Option/Alt+1 would create either highlight or underline
annotation.
d786454a3f
