Binder updates

[jsheunis]

This PR:

• Lets the binder button display for all datasets and not only for datasets with a github URL
• Updates the binder link to point to the main branch, related to datalad/datalad-binder@f65d9ae
• addresses a part of ENH: update everything Binder #302
• closes BUG: binder ink not displaying for all datasets #303
• closes Binder button should display for any dataset, not only for those with github urls #363

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (73521ee) 86.19% compared to head (067d2bf) 86.19%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #367   +/-   ##
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  Coverage   86.19%   86.19%           
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  Files          43       43           
  Lines        2709     2709           
=======================================
  Hits         2335     2335           
  Misses        374      374           

Flag	Coverage Δ
unittests	79.07% <ø> (ø)

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