Adding missing bindings for p6est functionality; Adding an example script that illustrated how to leverage p6est functionality

[amartinhuertas]

Ready to merge

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 6.66667% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 19.64%. Comparing base (c6db4f4) to head (7ee5eef).

❗ Current head 7ee5eef differs from pull request most recent head 1cbee79. Consider uploading reports for the commit 1cbee79 to get more accurate results

Files	Patch %	Lines
src/bindings/p6est_api.jl	0.00%	14 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
- Coverage   19.85%   19.64%   -0.22%     
==========================================
  Files           7        7              
  Lines        1264     1278      +14     
==========================================
  Hits          251      251              
- Misses       1013     1027      +14     

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