[DOCS] Add featuredetect link in README

[gedw99]

https://github.com/passkeydeveloper/featuredetect.passkeys.dev

To help with debugging. Reporting where users hit problems due to lack of features etc.

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UPD:

• add featuredetect link to README in Troubleshooting section

[egregors]

Yep, I saw this tool. It looks pretty useful, thanks!
And it looks like mobile Safari doesn’t have good support for all this stuff :///

[gedw99]

Inside _example, am thinking if we need some basic logging ?

Initially just outputting the "origin := fmt.Sprintf("%s://%s%s%s", proto, sub, host, originPort)" will help with when we wrap it with a Proxy.

[gedw99]

stuff

Yep, I saw this tool. It looks pretty useful, thanks! And it looks like mobile Safari doesn’t have good support for all this stuff :///

I know. Apple like closed gardens.