fix: export markdown file

[appflowy]

PR Checklist

• My code adheres to the AppFlowy Style Guide
• I've listed at least one issue that this PR fixes in the description above.
• I've added a test(s) to validate changes in this PR, or this PR only contains semantic changes.
• All existing tests are passing.

[appflowy]

fix #2839

[codecov]

Codecov Report

Merging #2841 (905f74a) into main (177f7c4) will increase coverage by 44.33%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##             main    #2841       +/-   ##
===========================================
+ Coverage   13.00%   57.33%   +44.33%     
===========================================
  Files         401      401               
  Lines       18665    18686       +21     
===========================================
+ Hits         2427    10714     +8287     
+ Misses      16238     7972     -8266     

Flag	Coverage Δ
appflowy_flutter_integrateion_test	54.97% <100.00%> (?)
appflowy_flutter_unit_test	13.00% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ppflowy_flutter/lib/plugins/document/document.dart	92.15% <100.00%> (+88.07%)	⬆️

... and 280 files with indirect coverage changes