Move Shift + Insert to shortcut

Move Shift + Insert to shortcut

Shift + Insert is used like a hot key for paste the selection, so it is more
logical move it to shortcut array instead of having special code for it.
---
 config.def.h |    1 +
 st.c         |   13 +++----------
 2 files changed, 4 insertions(+), 10 deletions(-)