feat: enhance template preRun and postRun options and add templating docs

[jahvon]

Summary

Variety of templating updates, including docs updates

Notable Changes

• Fixes docs generation for templates
• Adds content to the templating guide
• Accepts templating in the preRun and postRun fields
• Fixes handling of preRun and postRun args

[codecov]

Codecov Report

Attention: Patch coverage is 39.24051% with 48 lines in your changes missing coverage. Please review.

Project coverage is 37.32%. Comparing base (9a98046) to head (3c38fc3).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/templates/templates.go	54.16%	13 Missing and 9 partials ⚠️
types/executable/executable_md.go	0.00%	18 Missing ⚠️
internal/templates/form.go	38.46%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #177      +/-   ##
==========================================
- Coverage   37.38%   37.32%   -0.07%     
==========================================
  Files          81       81              
  Lines        5716     5769      +53     
==========================================
+ Hits         2137     2153      +16     
- Misses       3149     3181      +32     
- Partials      430      435       +5     

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