Add viewport tag to generated HTML file

[benjamin-bergia]

This relate to this issue.
When running elm-make, (and the same issue is present with elm-reactor), the generated html file doesn't contain any viewport meta tag.

Would it be possible to add one by default ? It would be very nice to have it on elm-reactor too.

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[ian-moore]

This would be nice. I could take a stab at a PR for this. I think the addition needs to be added here:

elm-make/src/Pipeline/Generate.hs

Line 157 in 2cf040a

H.meta ! A.charset "UTF-8"