Add and run prettier

[vil02]

This monster PR consists of two three steps/commits:

• adds and configures prettier in a similar way as in JavaScript,
• formats the code by running the command npm run style,
• adds a step, checking the formatting, into the CI.

When this will be merged, I will create another PR modifying the CI in such a way, that the formatting is checked (I guess @Panquesito7 will be needed to merge such PR).

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.97015% with 54 lines in your changes missing coverage. Please review.

Project coverage is 96.84%. Comparing base (c5b12db) to head (d137e41).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
data_structures/list/singly_linked_list.ts	79.71%	14 Missing ⚠️
data_structures/list/doubly_linked_list.ts	91.52%	10 Missing ⚠️
data_structures/queue/circular_queue.ts	84.09%	7 Missing ⚠️
data_structures/tree/binary_search_tree.ts	87.23%	6 Missing ⚠️
data_structures/stack/linked_list_stack.ts	75.00%	5 Missing ⚠️
search/interpolation_search.ts	82.35%	3 Missing ⚠️
data_structures/heap/heap.ts	97.05%	2 Missing ⚠️
data_structures/map/hash_map.ts	97.56%	2 Missing ⚠️
maths/fibonacci.ts	94.44%	1 Missing ⚠️
maths/hamming_distance.ts	50.00%	1 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #234      +/-   ##
==========================================
- Coverage   97.00%   96.84%   -0.16%     
==========================================
  Files          98       98              
  Lines        1800     1838      +38     
  Branches      346      348       +2     
==========================================
+ Hits         1746     1780      +34     
- Misses         54       58       +4     

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[raklaptudirm]

Add a CI for testing proper styling in this pull request too.