use markdown for notebook reports

[dberenbaum]

Fixes #537 and #546

Depends on iterative/dvc-render#129.

Screen.Recording.2023-05-05.at.4.15.17.PM.mov

Still needs:

• dependency on updated dvc-render
• tests
• cleanup image support

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.09 ⚠️

Comparison is base (29b95c3) 95.88% compared to head (5c98c3f) 95.79%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #558      +/-   ##
==========================================
- Coverage   95.88%   95.79%   -0.09%     
==========================================
  Files          43       43              
  Lines        2744     2735       -9     
  Branches      236      233       -3     
==========================================
- Hits         2631     2620      -11     
- Misses         66       69       +3     
+ Partials       47       46       -1     

Impacted Files	Coverage Δ
src/dvclive/live.py	91.18% <100.00%> (ø)
src/dvclive/report.py	96.03% <100.00%> (+1.64%)	⬆️
tests/test_report.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[daavoo]

This renders nicer and looks cleaner in the code 🚀

[dberenbaum]

Updated to render without creating any persistent markdown file