add static_assert

[matter123]

This PR adds support for the static_assert and _Static_assert keywords.

Why?

static_assert is currently (1.8.8) marked as entity.name.function when it is rather a function-like keyword, marking it as a keyword fixes the coloring.

Additionally, as #80 progresses this will cause issues if left unattended as static_assert is allowed in places where normal function calls are not.static_assert(1==1); is a completely valid C++ program (goodbolt).
As the distinction is made between function calls and function declarations, static_assert's insides may end up with undesirable coloring.

[jeff-hykin]

Something weird is going on with the
keyword.static_assert.cpp.c instead of
keyword.static_assert.c

The grammar class should have automatically fixed that so I'm going to look into what is going on

[jeff-hykin]

Took awhile to fix. In the textmate_tools the changes were being done as mutations, I changed it to be more of a functional style, all changes are done with a copy, and the copy is returned. I also fixed the other leftover .cpp values in the c syntax.