Mangrove alerts widget: show only years, instead of all months

[lhilarides]

There are too many months to show individually, so I think showing only years (from 2019 until the year of "today") is better

[mluena]

I've done a combination of both, all years at the bottom. And months on the top chart

[klongleywood]

I think it would be ok to just include the top chart with the fix of having only every few months labeled. What do you think @lhilarides