Add events tab

[niksirbi]

Closes #60

[codecov-commenter]

Codecov Report

Merging #72 (b150dbb) into main (c46e1bb) will increase coverage by 1.79%.
The diff coverage is 48.64%.

❗ Current head b150dbb differs from pull request most recent head 5940e17. Consider uploading reports for the commit 5940e17 to get more accurate results

@@            Coverage Diff             @@
##             main      #72      +/-   ##
==========================================
+ Coverage   32.99%   34.78%   +1.79%     
==========================================
  Files          12       13       +1     
  Lines         585      644      +59     
==========================================
+ Hits          193      224      +31     
- Misses        392      420      +28     

Impacted Files	Coverage Δ
wazp/callbacks/roi.py	17.17% <0.00%> (+0.31%)	⬆️
wazp/utils.py	22.69% <14.28%> (-0.38%)	⬇️
wazp/callbacks/events.py	32.50% <32.50%> (ø)
wazp/callbacks/home.py	42.85% <40.00%> (-0.48%)	⬇️
wazp/app.py	91.66% <100.00%> (+0.75%)	⬆️
wazp/pages/03_events.py	100.00% <100.00%> (ø)

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[niksirbi]

This is how the interface looks as of now.
A few remaining points until minimal functionality is achieved:

• Ensure that the maximum frame index for each video is not exceeded
• Ensure that no two events occupy the same frame index
• Add buttons for saving, loading, and deleting (as in the ROI page)