Update FileReader.__init__ implementation and lint code for flake8 compliance

[debpal]

Updated the CSV file reading logic in the FileReader.__init__ function, linted the entire pySWATPlus package, and added a GitHub Actions workflow to enforce code linting using flake8.

[zepholus]

In linting.yml, you're setting --max-line-length=127 for flake8, but in setup.cfg, rule E501 (line length) is being ignored. This makes the --max-line-length setting ineffective.

It's totally fine to enforce a max line length, but it's a bit unclear what the intended limit is. Is 127 a deliberate choice? I’ve typically seen values like 88 (Black’s default) or 100 in other projects (it's my first time linting, so I don't know which one is better).

[debpal]

In linting.yml, you're setting --max-line-length=127 for flake8, but in setup.cfg, rule E501 (line length) is being ignored. This makes the --max-line-length setting ineffective.

It's totally fine to enforce a max line length, but it's a bit unclear what the intended limit is. Is 127 a deliberate choice? I’ve typically seen values like 88 (Black’s default) or 100 in other projects (it's my first time linting, so I don't know which one is better).

@zepholus Yes, you're absolutely right — thanks for pointing that out! I had copied the linting config from another project and didn’t fully align the settings, so the --max-line-length=127 is currently ineffective due to E501 being ignored.

Since the GitHub Action passes, we can go ahead and merge this pull request. After that, feel free to push a follow-up change based on your preference — either enforce a specific line length (e.g., 88, 100, or 127), or keep ignoring E501. Totally up to you!