Add info about Backspace and Delete to the FAQ

Here is a modest attempt at cleaning it up a little bit. I changed a
few phrases that seemed awkward, but I think the content is the same.

--
Wolfgang Corcoran-Mathe

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
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Internal Server Error - Gitea: Git with a cup of tea and freedom
500 Internal Server Error

Gitea Version: 1.28.0+dev-505-g31b4d79a84