Add markerIndent and contentIndent to ListItem

[robinst]

This information is required for a renderer producing Markdown :).

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8cf87a3) 94.28% compared to head (ec66829) 94.30%.

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Additional details and impacted files

@@             Coverage Diff              @@
##               main     #303      +/-   ##
============================================
+ Coverage     94.28%   94.30%   +0.01%     
  Complexity      227      227              
============================================
  Files           124      124              
  Lines          3625     3633       +8     
  Branches        549      549              
============================================
+ Hits           3418     3426       +8     
  Misses          104      104              
  Partials        103      103              

Files	Coverage Δ
.../java/org/commonmark/internal/ListBlockParser.java	97.14% <100.00%> (ø)
...n/java/org/commonmark/internal/ListItemParser.java	95.45% <100.00%> (+0.45%)	⬆️
...rk/src/main/java/org/commonmark/node/ListItem.java	100.00% <100.00%> (ø)