✨ Added "startsWith" check to the match helper

[ramrami]

Added "startsWith" string comparison to the match helper.

I think this simple check will unlock and simplify a lot of use cases for theme developers:

Group logic when dealing with similar custom settings:

{{!-- Suppose layout could be: "List full", "List narrow", "Grid 2 cols", "Grid 3 cols", "Grid masonry" --}}
{{#match @custom.layout "startsWith" "Grid"}} 
    has-grid
{{/match}}

Check if a URL is external:

{{^match (url absolute="true") "startsWith" @site.url }} 
    is-external
{{/match}}

Simulate nested tags:

{{#match slug "startsWith" "hash-parent-tag-" }} 
    {{> template-parent }}
{{/match}}

Help implementing nested navigation:

{{#match label "startsWith" "--" }} 
    is-child-nav-item
{{/match}}

Add a badge to a navigation item:

{{#match label "startsWith" "[NEW]" }} 
    <span>{{t "NEW"}}</span>
{{/match}}

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• There's a clear use-case for this code change, explained below
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🤖 Generated by Copilot at 082c4f9

This pull request adds support for the startsWith operator to the match template helper, which allows matching data values against string prefixes. It also adds unit tests for the new operator in the match.test.js file.

[ramrami]

@ErisDS Any chance we can get this to upstream?