Proposal: `http.parse_link_header` (RFC 8288)

In the spirit of the existing `http.parse_content_disposition` that implements [RFC 2045](https://www.rfc-editor.org/rfc/rfc2045.html), I'd like to propose the addition of `http.parse_link_header` defined in [RFC 8288](https://www.rfc-editor.org/rfc/rfc8288.html). These are the headers that look like:

```
Link: ; rel="previous";
title="previous chapter"
```

This is common in HTTP APIs (Stripe, ACME, etc). It seems advantageous to me to have a single, well-tested version of this rather than having each client implement their own.