feat: Add if block support to example

[ianlewis]

Description:

Add an {% if var %} support to the template language example.

Related Issues:

Fixes #97

Checklist:

• Review the CONTRIBUTING.md documentation.
• Add a reference to a related issue in the repository.
• Add a description of the changes proposed in the pull request.
• Add unit tests if applicable.
• Update documentation if applicable.
• Add a note in the CHANGELOG.md if applicable.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 96.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.36%. Comparing base (3a5e21f) to head (1a4dfa6).

Files with missing lines	Patch %	Lines
parser.go	96.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #100      +/-   ##
==========================================
+ Coverage   87.66%   89.36%   +1.69%     
==========================================
  Files           3        3              
  Lines         373      395      +22     
==========================================
+ Hits          327      353      +26     
+ Misses         34       30       -4     
  Partials       12       12              

Files with missing lines	Coverage Δ
parser.go	93.15% <96.66%> (+1.21%)	⬆️

... and 1 file with indirect coverage changes