Updates help center documentation for enabling `Enter` to send for
the new default button text (`Ctrl` + `Enter` to send).
Also adds backticks to all references to the `Enter` key, so that
they are updated by `adjust_mac_shortcuts` for Mac keyboards;
and removes the table at the end of the article replacing it with
a simple tip for the `Shift` + `Enter` keyboard shortcut.
Fixes help center documentation that use or reference Mac keys
for keyboard shortcuts instead of non-Mac keys since these are
not updated for users with non-Mac keyboards, while the reverse
is true.
Fixes existing errors in the help center documentation where a
keyboard shortcut that has multiple keys is all one inline code
tag (e.g. `Ctrl + [`) instead of being separated into individual
inline code tags for each key (e.g. `Ctrl` + `[`).
Lauryn Menard
Rishi Gupta