feat(UI): Add UI setting playbackRateSliderStep

[PikachuEXE]

The new playback rate slider buttons can only be used to playback rate by 0.05 per click
So it would be great so that we can customize it

FreeTube using the player but lacking this setting makes it harder to update from 5.1 to 5.2 (where this new component introduced - #10134
FreeTubeApp/FreeTube#9487

[shaka-bot]

Bundle Size Report for PR #10516

File	HEAD	Base	Diff
controls.css	41.4 KiB (7.1 KiB)	41.4 KiB (7.1 KiB)	0.0 KiB
controls.modern.css	33.9 KiB (6.5 KiB)	33.9 KiB (6.5 KiB)	0.0 KiB
demo.compiled.debug.js	266.3 KiB (54.1 KiB)	266.2 KiB (54.1 KiB)	+0.1 KiB
demo.compiled.js	266.3 KiB (54.1 KiB)	266.2 KiB (54.1 KiB)	+0.1 KiB
demo.css	160.4 KiB (25.7 KiB)	160.4 KiB (25.7 KiB)	0.0 KiB
demo.modern.css	146.1 KiB (24.7 KiB)	146.1 KiB (24.7 KiB)	0.0 KiB
locales.js	45.2 KiB (11.2 KiB)	45.2 KiB (11.2 KiB)	0.0 KiB
receiver.compiled.debug.js	151.1 KiB (24.5 KiB)	151.1 KiB (24.5 KiB)	0.0 KiB
receiver.compiled.js	151.1 KiB (24.5 KiB)	151.1 KiB (24.5 KiB)	0.0 KiB
shaka-player.compiled-es2021.debug.js	1330.9 KiB (331.1 KiB)	1330.9 KiB (331.1 KiB)	0.0 KiB
shaka-player.compiled-es2021.js	700.5 KiB (236.4 KiB)	700.5 KiB (236.4 KiB)	0.0 KiB
shaka-player.compiled.debug.js	1630.4 KiB (376.7 KiB)	1630.4 KiB (376.7 KiB)	+0.0 KiB
shaka-player.compiled.js	817.9 KiB (268.5 KiB)	817.9 KiB (268.5 KiB)	0.0 KiB
shaka-player.dash-es2021.debug.js	993.4 KiB (252.1 KiB)	993.4 KiB (252.1 KiB)	0.0 KiB
shaka-player.dash-es2021.js	494.1 KiB (170.0 KiB)	494.1 KiB (170.0 KiB)	0.0 KiB
shaka-player.dash.debug.js	1214.4 KiB (285.7 KiB)	1214.4 KiB (285.7 KiB)	+0.0 KiB
shaka-player.dash.js	579.3 KiB (193.0 KiB)	579.3 KiB (193.0 KiB)	0.0 KiB
shaka-player.experimental-es2021.debug.js	1771.2 KiB (427.8 KiB)	1771.1 KiB (427.8 KiB)	+0.1 KiB
shaka-player.experimental-es2021.js	981.6 KiB (313.9 KiB)	981.5 KiB (313.9 KiB)	+0.2 KiB
shaka-player.experimental.debug.js	2161.3 KiB (486.0 KiB)	2161.1 KiB (486.0 KiB)	+0.1 KiB
shaka-player.experimental.js	1131.5 KiB (353.4 KiB)	1131.4 KiB (353.4 KiB)	+0.2 KiB
shaka-player.hls-es2021.debug.js	1014.8 KiB (255.3 KiB)	1014.8 KiB (255.3 KiB)	0.0 KiB
shaka-player.hls-es2021.js	521.3 KiB (178.5 KiB)	521.3 KiB (178.5 KiB)	0.0 KiB
shaka-player.hls.debug.js	1239.9 KiB (289.8 KiB)	1239.9 KiB (289.8 KiB)	+0.0 KiB
shaka-player.hls.js	609.7 KiB (203.0 KiB)	609.7 KiB (203.0 KiB)	0.0 KiB
shaka-player.transmuxer-worker.debug.js	238.2 KiB (54.7 KiB)	238.2 KiB (54.7 KiB)	-0.0 KiB
shaka-player.transmuxer-worker.js	95.9 KiB (31.4 KiB)	95.9 KiB (31.4 KiB)	0.0 KiB
shaka-player.ui-es2021.debug.js	1648.3 KiB (402.9 KiB)	1648.2 KiB (402.8 KiB)	+0.1 KiB
shaka-player.ui-es2021.js	920.3 KiB (297.9 KiB)	920.1 KiB (297.9 KiB)	+0.2 KiB
shaka-player.ui.debug.js	1987.2 KiB (454.5 KiB)	1987.0 KiB (454.5 KiB)	+0.1 KiB
shaka-player.ui.js	1051.0 KiB (333.9 KiB)	1050.8 KiB (333.9 KiB)	+0.2 KiB

[shaka-bot]

Incremental code coverage: 76.92%