Update PULL_REQUEST_TEMPLATE.md

[jjaime2]

Add note on using a diff checker when running pylint

Description

[TODO: describe, in-detail, what issue this PR addresses and how it addresses it. Link to relevant Github Issues.]

Testing procedure

[TODO: describe, in-detail, how you tested this. The procedure must be detailed enough for the reviewer(s) to recreate it.]

Before opening a pull request

• pre-commit run --all-files
• Run your code through pylint. pylint --recursive=y --rcfile=.pylintrc .. All warnings but fixme must be addressed.

Before Merging

• Squash & Merge