Add a simple spk lint command

[rydrman]

This command (for now) simply reads in the yaml file and applies any required templating to ensure that the yaml file is valid.

related to #531 & #531

[codecov]

Codecov Report

Merging #600 (8745cbe) into master (d5cbb70) will increase coverage by 1.29%.
The diff coverage is 0.00%.

❗ Current head 8745cbe differs from pull request most recent head ae33c5c. Consider uploading reports for the commit ae33c5c to get more accurate results

@@            Coverage Diff             @@
##           master     #600      +/-   ##
==========================================
+ Coverage   57.68%   58.97%   +1.29%     
==========================================
  Files         214      208       -6     
  Lines       15186    14690     -496     
==========================================
- Hits         8760     8664      -96     
+ Misses       6426     6026     -400     

Impacted Files	Coverage Δ
crates/spk-cli/group4/src/cmd_lint.rs	0.00% <0.00%> (ø)
crates/spk/src/cli.rs	0.00% <0.00%> (ø)
...spk-schema/crates/foundation/src/spec_ops/named.rs	50.00% <0.00%> (-16.67%)	⬇️
crates/spk-schema/crates/ident/src/format.rs	60.00% <0.00%> (-13.08%)	⬇️
crates/spk-schema/src/embedded_packages_list.rs	57.57% <0.00%> (-12.80%)	⬇️
crates/spk-storage/src/storage/mem.rs	62.93% <0.00%> (-7.37%)	⬇️
crates/spk-cli/cmd-test/src/cmd_test.rs	73.52% <0.00%> (-7.12%)	⬇️
crates/spk-storage/src/storage/repository.rs	85.41% <0.00%> (-4.06%)	⬇️
crates/spk-schema/src/v0/spec.rs	77.97% <0.00%> (-2.95%)	⬇️
crates/spk-solve/src/io.rs	42.08% <0.00%> (-1.72%)	⬇️
... and 71 more

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[jrray]

Looks useful, I've got a few ideas for lints that would catch common mistakes.