add buttons to control the viewport

this MR implements buttons to fix the current extent of the plot (fix_map_extent), restrict the data to the given extent (fix_lonlatbox) or resetting the options back to the default.

see psy-maps!49 (merged)

merged

assigned to @philipp.sommer

added 1 commit

• 6cbd0cf6 - enable the buttons in the right positions

Compare with previous version

enabled an automatic merge when the pipeline for 6cbd0cf6 succeeds

mentioned in commit 07378cfc