Add mpv configs

I'm surprised this was never here before. Oh well, gives me an excuse to
clean these up and comment them too.

.config/mpv/mpv.conf

@@ -0,0 +1,16 @@
+# I like normalizing at 100% volume and going up from there
+# 1000% is excessive but at least I'll never cap out
+volume-max=1000
+
+# My mpv usage is either on-disk media, or streamlink which does its own
+# caching, so we don't need to double cache.
+cache=no
+cache-pause=no
+demuxer-readahead-secs=1
+
+# Audio filter to try to normalize audio levels. Especially important for
+# Twitch where there's no defacto normal level to target
+af="dynaudnorm=g=5:f=250:r=0.9:p=0.5"
+
+# Put screenshots in my bespoke screenshot dir
+screenshot-directory=~/screenshot