Integrate sprig for improved templating

[mntn-xyz]

Currently templates are fairly limited, with only the built-in Go template functions and the one sortPosts helper function. I am working on templates for my own site and needed something equivalent to sprig's hasPrefix, as I wanted to display every post under a specified path, including posts from nested subdirectories. (I am working on making Hugo branch and leaf nodes work; these currently don't seem to work beyond the first level.)

Sprig provides functions for displaying the current date, string manipulation, and plenty more. This would be an easy way to expand the functionality of the Gemtext templates. The chief downside is that it adds a few dependencies.

[tdemin]

@mntn-xyz this looks good, thank you!

It looks like you haven't run go mod tidy yet? Building/testing the code right now will fail because of go.sum / go.mod mismatch.

PS: I initially thought about adding Sprig in because I wanted to write as little custom helpers as possible, but ended up not doing it. :P

[mntn-xyz]

Thanks, I am still new to go... the syntax is straightforward, but I need to read up on the tooling!