Add clj-kondo config with improved hook for >defn

[MrEbbinghaus]

Finally, the PR mentioned in https://github.com/fulcrologic/fulcro/pull/492.

I tested it in my project:

❯ clj-kondo --copy-configs --dependencies --lint "$(clojure -Spath)"
Imported config to .clj-kondo/com.fulcrologic/guardrails. To activate, add "com.fulcrologic/guardrails" to :config-paths in .clj-kondo/config.edn.

TODO: We can kick the guardrails parts from the fulcro clj-kondo config.

---

Original PR: fulcro

The current clj-kondo hook for >defn produces a false positive when using argument predicates ("such that").

This would fail because the current implementation counts everything before =>:

(>defn my-fn [x]
  [::x | #(pos? x) => any?] 
  x)

---

I took the chance and added some more checks to the gspec validation.

gspec reference: [arg-specs* (| arg-preds+)? => ret-spec (| fn-preds+)? (<- generator-fn)?]

What errors are caught?

• Missing =>
• Missing ret-spec
• | present but no arg-preds
• number of arg-specs is not equal to number of arguments

@holyjak Maybe you want to review this as well?

[awkay]

cool