feat: Add shortcode for the latest version of NGINX Gateway Fabric

[ADubhlaoich]

Proposed changes

This commit adds a new shortcode to the layouts folder to store a string representing the latest version of NGINX Gateway Fabric. This means that instead of updating each file individually during a new release, only the shortcode file needs to be modified.

It clarifies the versioning for documentation, which makes it easier to review - and also reduces the amount of drift when updating, in the case that a reference was overlooked. There may be old references that need to be updated to use this shortcode.

Closes #199

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[sjberman]

Check for any 1.5.1 instances as well, I think those were seen in an includes for the install docs.

[mjang]

Question: while I like this idea, I think this looks like "nesting includes," which our style guide suggests we avoid. @travisamartin WDYT?

[ADubhlaoich]

Question: while I like this idea, I think this looks like "nesting includes," which our style guide suggests we avoid. @travisamartin WDYT?

Ooh, I forgot about this. I think it was largely to avoid situations where skeletons of pages would be built in refraction: this is nested re-used content, but the scope is probably the tightest you could get for an include. Subsequent to affected pages are watching the version string increment as opposed to reviewing 16 separate files.

[mjang]

Question: while I like this idea, I think this looks like "nesting includes," which our style guide suggests we avoid. @travisamartin WDYT?

Ooh, I forgot about this. I think it was largely to avoid situations where skeletons of pages would be built in refraction: this is nested re-used content, but the scope is probably the tightest you could get for an include. Subsequent to affected pages are watching the version string increment as opposed to reviewing 16 separate files.

As I think I implied, I'd welcome this kind of exception to the style guide.

[JTorreG]

Question: while I like this idea, I think this looks like "nesting includes," which our style guide suggests we avoid. @travisamartin WDYT?

Ooh, I forgot about this. I think it was largely to avoid situations where skeletons of pages would be built in refraction: this is nested re-used content, but the scope is probably the tightest you could get for an include. Subsequent to affected pages are watching the version string increment as opposed to reviewing 16 separate files.

As I think I implied, I'd welcome this kind of exception to the style guide.

I don't consider a variable shortcode inside an include a nested include, as the real content of the variable can be "guessed" or at least understood without having to open the source file with the actual value.

The issue with nested variables is obfuscating the real content to the point that it's not possible to effectively review the document

[mjang]

To clarify, I've opened #207