Fix some code quality issues

[pnijhara]

• Remove unused variables
• Fix dangerous default argument
• Use literal syntax instead of function calls to create the data structure

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Find the other issues found here - https://deepsource.io/gh/pnijhara/gitsome/issues/?category=all

This PR also adds .deepsource.toml configuration file to run DeepSource analysis on the repo with. Upon enabling DeepSource, the analysis will run on every PR and commit to detect 560+ types of issues in the changes — including bug risks, anti-patterns, security vulnerabilities, etc.

To enable DeepSource analysis after merging this PR, please follow these steps:

1. Signup on DeepSource with your GitHub account and grant access to this repo.
2. Activate analysis on this repo here.

You can also look at the docs for more details. Do let me know if I can be of any help!

[codecov-io]

Codecov Report

Merging #176 into master will decrease coverage by 41.89%.
The diff coverage is 42.85%.

@@             Coverage Diff             @@
##           master     #176       +/-   ##
===========================================
- Coverage   95.09%   53.19%   -41.90%     
===========================================
  Files          34       86       +52     
  Lines        2119     6593     +4474     
===========================================
+ Hits         2015     3507     +1492     
- Misses        104     3086     +2982     

[Watemlifts]

Code quality fixed