Scalable UI #156

[kalkih]

Adds a new theme variable to adjust the scale of the card UI, this affects most of the cards elements and dimensions.

New theme variable is: --mini-media-player-scale and defaults to 40px.
The value is basically the row height, each row of the card is allowed to take up this much height and the UI is scaled accordingly.

This variable can be set either in the user's theme which will apply it to all mmp cards or with card-mod in the :host selector to target individual cards.

# user-theme
mini-media-player-scale: 50px

# card-mod example
...card config
style: |
  :host {
    --mini-media-player-scale: 50px;
  }

Unsure if we should add this as a card option instead of as a theme variable, and if we should keep the value as pixels or change it to percentage, scale (e.g. 2, 2.5, 0.75) or any other unit, would appreciate feedback regarding this.

Closes #156

[kalkih]

Added support for setting scale both through a config option and through theme variable.
Card option (if set) will override theme variable.

I also changed from a px value to a modifier value where default is 1 or "1.0".

# user theme variable
mini-media-player-scale: 1.25

# card-example
type: custom:mini-media-player
...options
scale: 0.75