Replacing standard `box-sizing` with MediaWiki's Less mixin, which also
features prefixed properties for older browsers like Firefox 28 and below.
Change-Id: Iafb88b192045fb7df6bbe6954a166a198d04c5cf
Due to pixel rounding errors when relying on `em` as base size unit,
the circle isn't always perfectly round and as a result /not/ a circle.
Adding `min-width` and `min-height` ensures the intended layout similar
to Ie61e7303e446 in OOjs UI's ToggleSwitchWidget.
Also aligning `:hover` unread color to OOjs UI progressive button's
`:hover`.
Bug: T141504
Change-Id: Idf130947e8e61a68819e3ac9ba3cb1e105e65370
Also add border-box to prevent the circle from appearing
to grow when a border appears.
Bug: T126214
Change-Id: Id5e89ff87759c4ae44851d5ad3061230a0e59ff0
Allow for mark read and mark unread through the side button, and
change its style according to spec in the ticket.
Bug: T126214
Change-Id: I78a93c0545bbe2d7c11a0c62557cd2e97e9d3866