mouse shortcuts: don't hardcode selpaste

Because selpaste is activated on release, a release flag was added to
mouse shortcuts which controls whether activation is on press/release,
and selpaste binding to button2 was moved to config.h .

button1 remains the only hardcoded mouse button - for selection + copy.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea and freedom
500 Internal Server Error

Gitea Version: 1.28.0+dev-505-g31b4d79a84