Path component in client_id considered optional

According to https://indieauth.spec.indieweb.org/#client-identifier

> Client identifier URLs ... MUST contain a path component

Example clients which provide no path component in client_id:

1. indiebookclub.biz
2. indigenous.realize.be (Indigenous for Android, as of 2020-06-16)
3. omnibear.com
4. teacup.p3k.io

It is understood that most IndieAuth servers permit clients with valid-in-common-usage client_ids.

**Suggestion**: modify the spec to match the common usage.

Start with the client identifier section of the IndieAuth specification linked in the issue, then review the three existing comments and the listed client examples. Determine the intended normative change and update the specification so its client_id requirement matches the resolved decision, with the examples and requirement remaining consistent.

Written by the indexing model from the issue text.