add gitignore
Fix compile warnings

```
cc -c -I./include -Wall -Wextra -fPIC -pedantic  src/fab.c
src/fab.c: In function ‘make_format’:
src/fab.c:15:5: warning: ISO C90 forbids mixed declarations and code [-Wpedantic]
     size_t count = esc_size;
     ^
src/fab.c: In function ‘rgb_to_xterm’:
src/fab.c:217:5: warning: ISO C90 forbids mixed declarations and code [-Wpedantic]
     int best_match = 0;
     ^
```