MAINT: reduce hours stefan, clarify lead maintainer

[sappelhoff]

• Reducing my hours due to upcoming commitments that won't allow me to stay involved as much as I was
• Based on internal discussions among maintainers, the role of "lead maintainer" will now be rotating among BIDS maintainers

The role description of what a "lead maintainer" is/does and how we rotate that responsibility should become part of the Maintainers Guide.

Furthermore, the content in the "Maintainers Group" section of the DECISION_MAKING.md document (edited here) should be migrated to the Maintainers Guide, once it's been merged, see:

• [DOC] add maintainers guide #1770

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.04%. Comparing base (898ea86) to head (9142ec9).
Report is 258 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1843   +/-   ##
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  Coverage   88.04%   88.04%           
=======================================
  Files          16       16           
  Lines        1380     1380           
=======================================
  Hits         1215     1215           
  Misses        165      165           

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[ericearl]

@sappelhoff Looks great, and thanks for fixing those little typos too!