Naive CEL validation example

[clux]

for #1367 and kube-rs/website#53
was testing it locally against k3d 1.27 (this one is a main run fn and is not tested on CI atm)

[codecov]

Codecov Report

Merging #1372 (35fc481) into main (289c501) will increase coverage by 0.1%.
Report is 1 commits behind head on main.
The diff coverage is 0.0%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1372     +/-   ##
=======================================
+ Coverage   72.1%   72.1%   +0.1%     
=======================================
  Files         75      75             
  Lines       6436    6435      -1     
=======================================
  Hits        4635    4635             
+ Misses      1801    1800      -1     

Files	Coverage Δ
kube-derive/src/lib.rs	0.0% <ø> (ø)
kube-derive/tests/crd_schema_test.rs	100.0% <ø> (ø)
kube-derive/src/custom_resource.rs	13.7% <0.0%> (+0.1%)	⬆️