Rework layout of widgets and add status bar

[goanpeca]

Fixes #69

[codecov]

Codecov Report

❌ Patch coverage is 94.23077% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.97%. Comparing base (d5bba24) to head (9d24f6f).
⚠️ Report is 106 commits behind head on main.

Files with missing lines	Patch %	Lines
napari_plugin_manager/qt_plugin_dialog.py	94.23%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #98      +/-   ##
==========================================
- Coverage   93.09%   92.97%   -0.12%     
==========================================
  Files          10       10              
  Lines        1781     1780       -1     
==========================================
- Hits         1658     1655       -3     
- Misses        123      125       +2     

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