precise-volume plugin fixes & updates

[Araxeus]

Adds a HUD that show current volume

it is displayed when volume percentage change, and fade out after a second

If video is disabled (hide-video plugin enabled)

HUD is displayed in the navbar since its pretty much the only place that is consistently visible
('playbar' have no space for elements when window is small)

Screenshot with hide-video

If video is enabled

HUD is displayed in the top left corner of the video player.
also works when minimized (video is shown in mini-player, volume control and hud works from there)

Screenshot with video

Screenshot with mini-video

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Sidenote :
I know there is utils.elementFromFile etc, buts since the element is so small, it's much shorter to just directly use Element.insertAdjacentHTML (its just one line of html)

Fixed various bugs by using native youtube api to change the volume

• youtube overriding precise volume on song start or randomly while playing
• video muting itself when volume<3
• video volume rounding to multiples of 5 on start

Other misc fixes

• Fixed plugin rewriting config on each volume step (by having a 1500 millisecond timeout before writing)
• use window.load event from front instead of webContents.did-finish-load event from back
  • [preload.js] once - remove addEventListener override
  • [front.js] on - inject custom HUD based on $(#main-panel).style.display == none(hide-video plugin enabled)

[th-ch]

Looks good, thanks for the improvement!