AdEx Theme(s) init

[ivopaunov]

We need to do as much as possible by modifying the theme of the components in order to use as less as possible custom styles.

Currently we have only light theme so there is no point making multi theme atm as this can be updated easy in the future.

Add mantine theme for matching AdEx design (not final here). With components overriders as here

[ivopaunov]

Just basic cfg + examples for start - we will add whatever we need as the work progress. We don't have final design anyway