Material dialog specific variables

`$mt-dialog-margin-ratio`

Type: number

Default value: $theme-margin-ratio

Computed value: 0.6

`$mt-dialog-field-height-ratio`

Type: number

Default value: $theme-field-height-ratio

Computed value: 0.7

`$mt-dialog-z-index`

Type: number

Default value: $z-index-Dialog

Computed value: 40

`$mt-dialog-background-color`

Type: color

Default value: $theme-secondary-alternative-background-color

Computed value: #ffffff

`$mt-dialog-overlay-background-color`

Type: color

Default value: $theme-overlay-background-color

Computed value: rgba(33, 33, 33, 0.26)