Establish community convention for "side-effecting"-only requires

[borkdude]

Please chime on this discussion:

clj-kondo/clj-kondo#241

After processing the feedback, we can extract a style guide "rule" from this.

[bbatsov]

Would you be interested in distilling a rule for this now that dust has settled?

[borkdude]

@bbatsov The convention that clj-kondo ended up adopting:

If a namespace has been required without :refer or :alias then it is assumed to be required for side effects and will not be reported as unused.