chore: group docusaurus dependencies

[WilliamBergamin]

Summary

This PR introduces the same dependabot configuration for the docs/ directory as bolt-python in #1155

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.59%. Comparing base (d39b329) to head (034f535).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2227   +/-   ##
=======================================
  Coverage   81.59%   81.59%           
=======================================
  Files          19       19           
  Lines        1646     1646           
  Branches      464      464           
=======================================
  Hits         1343     1343           
  Misses        194      194           
  Partials      109      109           

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