Formatting fixes, Background images and viewport control buttons
Changed
- migrate to psyplot-plugin-template, see [!64 <https://codebase.helmholtz.cloud/psyplot/psy-view/-/merge_requests/64]{.title-ref}__
- set minimum version for psyplot to 1.5.0
Added
- Background image options, see [!65 <https://codebase.helmholtz.cloud/psyplot/psy-view/-/merge_requests/65]{.title-ref}__
- add buttons to control the viewport, , see [!66 <https://codebase.helmholtz.cloud/psyplot/psy-view/-/merge_requests/66]{.title-ref}__