Idea: Roll out 'PR labeler' GitHub action to all pipeline (and modules) via template

[jfy133]

Description of feature

As per here: nf-core/modules#9822

@ewels found in another place a GitHub action that adds labels to PRs based on the size LoC.
The idea is we could use it to see if these labels can help the community reduce the size of PRs and thus promote faster reviews.

This is part of the solutions discussed at the nf-core retreat 2025: https://nf-co.re/blog/2025/retreat-2025#improving-review-and-development-practices

I've added the workflow to:

• modules: Experiment: Add GitHub Actions workflow for PR size labeling modules#9822 (to be removed/evaluated after a month)
• createtaxdb: Add PR labeller for estimating size of PRs createtaxdb#148
• funcscan: Add PR labeller for marking PR size funcscan#514
• mag: Add PR labeller workflow to report size of PRs mag#972
• taxprofiler: Add the PR size labeller action for testing taxprofiler#681

As experiments to see how well it works.

I open this issue to track suggestions for further configurations/tweaks as people bring them up etc.

[jfy133]

@mashehu suggested ignoring snapshot changes in modules: https://github.com/nf-core/modules/pull/9822/changes/BASE..5af001fc210b0b0d1d4d0801e0c18dac64eca586#r2753868721

[jfy133]

@prototaxites suggested: nf-core/mag#972 (comment)

Is it worth making this ignore the "linguist-generated" nf-core modules and subworkflows file changes that are listed in .gitattributes (https://github.com/nf-core/mag/blob/main/.gitattributes)?

I would like to think that changes to external nf-core code should not count towards PR size labelling