libraries/compile-examples: support YAML-format sketch-paths input value

[per1234]

The other two inputs that accept lists: libraries and platforms, support the value being a string in YAML format, following the precedent established by GitHub for their workflows.

For consistency, it makes sense to also support YAML format for the action's sketch-paths input.

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Demonstration of how the arduino-libraries/ArduinoIoTCloud repository's workflow would look if it used the new format:
https://github.com/per1234/ArduinoIoTCloud/commit/28af61b7efed26115803c565e173713123c221f5#diff-1ab188640fc440a6dba62ef93d03def2

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The old Bash array style space-separated list format is still supported and the default behavior of using the examples folder remain the same, so this change is backwards compatible.

[codecov-commenter]

Codecov Report

Merging #74 into master will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##            master       #74     +/-   ##
===========================================
  Coverage   100.00%   100.00%             
===========================================
  Files            6         2      -4     
  Lines         2486      1372   -1114     
===========================================
- Hits          2486      1372   -1114     

Impacted Files	Coverage Δ
...ompile-examples/compilesketches/compilesketches.py	100.00% <100.00%> (ø)
...ples/compilesketches/tests/test_compilesketches.py	100.00% <100.00%> (ø)
...t-size-trends/reportsizetrends/reportsizetrends.py
.../report-size-deltas/tests/test_reportsizedeltas.py
libraries/report-size-deltas/reportsizedeltas.py
...ds/reportsizetrends/tests/test_reportsizetrends.py

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[aentinger]

LGTM 👍 Thank you @per1234 🚀