terminfo: add Tc, setrgbf and setrgbb capabilities

These extensions are used by tmux and neovim, in order to make use
of 24-bit colors without facing the problems that plague the `RGB`
capability.

This should allow 24-bit colors to work "out of the box" in tmux,
without the usual workaround of adding:

    set-option -ga terminal-overrides ",foot*:Tc"

...to ~/.tmux.conf.

See also:

* 18fe2e8dfa (commitcomment-31373962)
* f83c25942d/runtime/doc/term.txt (L123-L139)
* b1a8c0fe02/CHANGES (L988-L989)

Closes #615

CHANGELOG.md

@@ -32,6 +32,10 @@
 ### Added
 
 * `--log-level=none` command-line option.
+* `Tc`, `setrgbf` and `setrgbb` capabilities in `foot` and `foot-direct`
+  terminfo entries. This should make 24-bit RGB colors work in tmux and
+  neovim, without the need for config hacks or detection heuristics
+  (https://codeberg.org/dnkl/foot/issues/615).
 
 ### Changed
 ### Deprecated

foot.info

@@ -24,6 +24,7 @@ foot+base|foot base fragment,
     xenl,
     AX,
     XT,
+    Tc,
     cols#80,
     it#8,
     lines#24,
@@ -255,6 +256,8 @@ foot+base|foot base fragment,
     rs1=\Ec,
     rs2=\E[!p\E[?3;4l\E[4l\E>,
     sc=\E7,
+    setrgbb=\E[48\:2\:\:%p1%d\:%p2%d\:%p3%dm,
+    setrgbf=\E[38\:2\:\:%p1%d\:%p2%d\:%p3%dm,
     sgr0=\E(B\E[m,
     sgr=%?%p9%t\E(0%e\E(B%;\E[0%?%p6%t;1%;%?%p5%t;2%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;%?%p7%t;8%;m,
     sitm=\E[3m,