Update configured Mui breakpoints to include xl

[frano-m]

Mui default breakpoints range from xs to xl. Initial configuration of findable-ui required the use of xs to lg. Some applications now use a custom mid-range breakpoint. We should probably update the default configured breakpoints in findable-ui to accomodate this custom mid-range bp by shuffling the upper bp and utilising the xl key.

This will be a breaking change and an assessment of any styles using a breakpoint may need to be updated as part of this ticket.