adding minpin to list of pinning service providers

[gregwalters]

Describe your changes

Adding https://minpin.me to the list of pinning service providers.

Files changed

• docs/how-to/work-with-pinning-services.md

What issue(s) does this address?

MinPin exists but isn't in the list of providers that can be used and with this, it will be.

Does this update depend on any other PRs?

Nope.

Checklist before requesting a review

• Passing the beta version of the Check Markdown links for modified files check. Action results can be viewed here.

Checklist before merging

• Passing all required checks (The beta Check Markdown links for modified files check is not required)