feat: use custom slugs for permalinks if set

[greatislander]

Right now permalinks are ALWAYS generated based on the a slugified version of the title. However, in some instances users may want to specify a different slug, for example to have a page for "Equitable Digital Systems" at /eds. This PR modifies generatePermalink so that it will use a slug in the front matter data if it exists rather than slugifying the title.

[codecov]

Codecov Report

Merging #218 (26034b6) into main (d4f5592) will not change coverage.
The diff coverage is 100.00%.

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##             main     #218   +/-   ##
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  Coverage   98.28%   98.28%           
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  Files          13       13           
  Lines         641      641           
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  Hits          630      630           
  Misses         11       11           

Files	Coverage Δ
src/utils/generate-permalink.js	100.00% <100.00%> (ø)

[chosww]

Thanks @greatislander for this fix, this fix makes sense; however, we should update the comment in projects.11ty.data about the permalink. With this fix, permalink always get overwritten by output of generatePermaLink util function, even when we don't have to call the function. This fix looks great and we can go with this approach if you think it's better, but I also thought about different approach that's more accurate for what the comment said in projects.11ty.data file, and here's the approach that works:

eleventyComputed: {
        langDir: data => data.supportedLanguages[data.locale].dir,
        /* Configure navigation */
        eleventyNavigation: {
        /* Build a permalink using the title and language key if a custom permalink was not supplied. */
        ...(data => !data.permalink ? {
            permalink: data => {
                const locale = data.locale;
                return generatePermalink(data, "projects", i18n._(locale, "projects"));
            }
        } : {})
    }

[greatislander]

@chosww We will definitely update the comment. Your proposed approach gets complex for content editors when working with multiple languages. They need to know to enter the full slug including translated content type and locale slug otherwise it won't match the expected pattern— so if we are allowing a full permalink override then content editors need to know that the French equivalent of /projects/equitable-digital-systems is /fr/projets/systemes-numeriques-equitables/, not just /projects/systemes-numeriques-equitables. That leaves lots of potential for user error. The part that people need to customize is the title of the content so I think this solution is simplest.

[chosww]

Thanks for the explanation @greatislander, that makes sense 👍