Style: Implement lintr

[m-kolomanski]

Issue

Closes #40

Description

The details are also up for discussion, but I believe it is necessary to define how the code should be written, so we can keep it clean, consistent and easily understandable. We can automate this process and make sure the code always adheres to the rules by utilizing lintr.

For setup in IDE, please follow this guide.

For Rstudio, in addition I personally recommend checking the Provide R style diagnostics in the Tools -> Global Options -> Code -> Diagnostics. This will display all linter issues within the editor.

For VSCode, I personally recommend installing Error Lens extension for better highlighting.

Definition of Done

• [x] basic configuration for lintr implemented
• [ ] details of lintr rules discussed and implemented in configuration
• [ ] current codebase adheres to applied guidelines

[m-kolomanski]

Things to discuss regarding the details of implementation:

• Style guide -> is there any style guide we want to adhere to? The standard is tidyverse guide, but we can change things to adhere to our preferences (I am not a fan of couple of rules included), as long as we are consistant.
• Line length -> I have bumped it from 80 to 100 due to personal preference. I think even going to 120 is fine.
• Assignment -> we can either use = or <- for variable assignment, using both is messy. Tidyverse guide suggests <-, I personally dislike it and prefer =. We can do whatever, as long as we are being consistant.