Add linting step for extraneous elements in SVGs

[ericcornelissen]

Issue: Closes #3223

Description

This adds a new custom linter to the SVG linter (npm run svglint) that checks if SVGs start with <svg and end in </svg> (allowing for a single newline).

It works as expected, as illustrated by this build failure, which was fixed in 498561c (the icon had one trailing whitespace).

Suggested regarding the error message and reporter name are welcome 😄

[PeterShaggyNoble]

Other than the change above, this looks good to go to me. When I get around to reviewing the complete markup for all our icons, we may need to expand on this to include other checks.

Although, if we could somehow automate fixing niggly little things like this, that, I think, would be a better solution.

[ericcornelissen]

Other than the change above, this looks good to go to me.

Changed it 👍 Thanks for the suggestion

When I get around to reviewing the complete markup for all our icons, we may need to expand on this to include other checks.

I'd suggest defining a separate custom check for each of those.

Although, if we could somehow automate fixing niggly little things like this, that, I think, would be a better solution.

Even if we do that, it's still useful to have this 1) just in case and 2) for anyone to check their contributions locally.

[PeterShaggyNoble]

This looks good to me now, Eric 👍 As it involves a change to our linting, though, let's get one of the other @simple-icons/maintainers to throw an eye over it, too.

I'd suggest defining a separate custom check for each of those.

My plan at the moment is to identify the problems in our existing icons and open an issue with a list for discussion on which ones we want to fix and which ones we want to add tests for (at which stage we can discuss the implementation also) then submit a PR to manually fix those icons and then begin working on the linting separately.

[runxel]

Thank you for the work! It looks great and is a fine addition [insert star wars meme here] 👍