Basic traverse and linter rules

[tkers]

This needs some improvement around the Module | Syntax parts still, as a lot of functions could be merged.

[codecov[bot]]

Codecov Report

Merging #78 into master will decrease coverage by 3.21%. The diff coverage is 11.47%.

@@            Coverage Diff             @@
##           master      #78      +/-   ##
==========================================
- Coverage   90.55%   87.34%   -3.22%     
==========================================
  Files          31       32       +1     
  Lines        1440     1501      +61     
  Branches      227      241      +14     
==========================================
+ Hits         1304     1311       +7     
- Misses        118      172      +54     
  Partials       18       18

Impacted Files	Coverage Δ
packages/delisp-core/src/index.ts	100% <100%> (ø)	:arrow_up:
packages/delisp-core/src/linter.ts	12% <12%> (ø)
packages/delisp-core/src/syntax-utils.ts	52.74% <8.57%> (-27.61%)	:arrow_down:

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[davazp]

It would be nice to find a more functional-friendly way of writing rules. The visitor patterns rely too much on the execution order and keeping state. It's quite imperative.

It would be interesting if we can compare with other implementations at some point.

But this looks good, with a bit of clean up and tests we can merge it. It should be easy to maintain.