fix: Allow out-of-bound insertions

[koubaa]

it partially worked when inserting to card sets, except it always assumed that insertions go to the end. Extend support to insertions into keywords and use the specified index

fixes #956

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.72%. Comparing base (311c87b) to head (892e957).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #960   +/-   ##
=======================================
  Coverage   78.72%   78.72%           
=======================================
  Files          79       79           
  Lines       10681    10681           
=======================================
  Hits         8409     8409           
  Misses       2272     2272           

Flag	Coverage Δ
keywords	99.63% <ø> (ø)
run	49.19% <ø> (ø)
unittests	78.25% <ø> (ø)

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