The Keyboard tab in Tools > Customize was using the underline ("U")
icon, which is confusing. Add a new keyboard icon and reference it.
SVG icons added for colibre_svg and colibre_dark_svg themes; PNG
versions generated for colibre and colibre_dark themes.
Change-Id: I4fbbc0f667ae4d90a19f36b7d72718dbbd6697d4
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/204348
Tested-by: Jenkins
Reviewed-by: Heiko Tietze <heiko.tietze@documentfoundation.org>