Focusing header editors was hardcoded as integers which only worked with
the default ui. If a user changed the UI to, for example, put CC as a
field below "to", FocusSubject would focus the CC field instead of the
subject. This commit reuses and modifies the function FocusEditor to
generalize the focusing of header editors - which can now be called by
name via FocusEditor(name string)
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>