commitmsg: add spell checking to the summary field
Use the SpellCheckLineEdit to provide spellcheck capabilities in the
summary field. This is a long-desired feature that was made possible
by "faking" a QLineEdit by forcing a QTextEdit to display a single line
only.
http://blog.ssokolow.com/archives/2022/07/22/a-qlineedit-replacement-with-spell-checking/
Closes #633
Closes #1070
Suggested-by: Pius Raeder @Myz via github.com
Suggested-by: Peter Jensen @peter-jensen via github.com
Signed-off-by: David Aguilar <davvid@gmail.com>