doc + meson.build: update information about foot.ini, small cleanup

- foot.ini.5: mention location of example config file
- foot.1: replace outdated (or incomplete) information about the
  location of the config file with references to foot.ini.5
- foot.1 and foot.ini.5: conform to scdoc specification, thus surround each
  header with (at least) one blank line. additionally consistently use exactly
  one line before/after each header (was sometimes two before)
- foot.1: some parts of the keybindings had their own section, move into
  KEYBOARD SHORTCUTS section
- foot.1: move EXIT STATUS section to the end where it is commonly found
- foot.1: copy information about config file handling from the beginning of
  foot.ini.5 into the CONFIGURATION section of foot.1
- INSTALL.md: foot.ini is no longer included in the documentation
- meson.build: do not bundle foot.ini with documentation anymore, see also
  https://codeberg.org/dnkl/foot/pulls/1015

Closes #1002

INSTALL.md

@@ -149,8 +149,8 @@ Available compile-time options:
 | `-Ddefault-terminfo`                 | string  | `foot`                | Default value of `TERM`          | none               |
 | `-Dcustom-terminfo-install-location` | string  | `${datadir}/terminfo` | Value to set `TERMINFO` to       | None               |
 
-Documentation includes the man pages, the example `foot.ini`, readme,
-changelog and license files.
+Documentation includes the man pages, readme, changelog and license
+files.
 
 `-Ddefault-terminfo`: I strongly recommend leaving the default
 value. Use this option if you plan on installing the terminfo files