builtin.conf: add --hdr-peak-percentile=99.995 to gpu-hq

This is higher quality but comes with a slight performance hit,
especially for weaker iGPUs, so I don't want to enable it out of the box
even when --hdr-compute-peak=auto.

DOCS/interface-changes.rst

@@ -32,6 +32,7 @@ Interface changes
     - change `--subs-with-matching-audio` default from `no` to `yes`
     - change `--subs-fallback` default from `no` to `default`
     - add the `--hdr-peak-percentile` option
+    - include `--hdr-peak-percentile` in the `gpu-hq` profile
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

etc/builtin.conf

@@ -51,6 +51,7 @@ scale=spline36
 cscale=spline36
 dscale=mitchell
 dither-depth=auto
+hdr-peak-percentile=99.995
 hdr-contrast-recovery=0.30
 correct-downscaling=yes
 linear-downscaling=yes