We were using these hollowed out arrows characters (⇽ , ⇾) in a few
places, these were inconsistent with the solid up and down arrow
characters (↑ , ↓) we use otherwise. This commit replaces them
everywhere in the codebase.
Fixes: #11573.
This moves help_table to informational-overlays.scss, replaces "," with
"or" and "P" with "shift + p" in order to be more clear and legible
this also improves the styling of the text.
Also adds relevant tests and documentation. We currently
do not narrow to a new topic, and instead just narrow to
the stream. Similarly, we do not narrow to a PM if any of
the recipients are invalid.
This should make it easier to find the templates that are actually
part of the core webapp, instead of having them all mixed together
with the portico pages.