Don't check for email addresses in verbatim code

[norswap]

Small thing, but with this input:

    go install github.com/golangci/golangci-lint/cmd/golangci-lint@v1.43.0

(So this instruction in a markdown code code block.)

you get lychee output:

✗ github.com/golangci/golangci-lint/cmd/golangci-lint@v1.43.0 (Unreachable mail address: github.com/golangci/golangci-lint/cmd/golangci-lint@v1.43.0)

Which is obviously not the desired outcome. Verbatim blocks should probably be ignored.

[lebensterben]

This is a bug obviously...

the domain part of an email address (those characters after '@'), can be any alphanumerical character or an '-'. With exception that:

• '-' cannot be the first or last character
• top level domain cannot be all numerical characters.

"0" is all numerical, so it cannot be a top level domain, and thus it cannot be an email address.

[mre]

@norswap thanks for the bug report. This is an issue in linkify. robinst/linkify#29
@lebensterben good input. Is there a spec where these rules are defined? Can you mention it in the linkify issue above?

[mre]

In general I think the verbatim part is fine but the e-mail address detection needs to be improved. This line would not show up if the false-positive was filtered out correctly.

[mre]

Excluding code blocks will be tackled in #523.

[mre]

This gets ignored in the latest master now. 🎉
If I have an input file like this called test.md:

Some content.
```
go install github.com/golangci/golangci-lint/cmd/golangci-lint@v1.43.0
```
Other test content

and I call lychee, the code block will be ignored by default:

❯❯❯ lychee test.md
🔍 0 Total ✅ 0 OK 🚫 0 Errors

The old behavior can be restored with --include-verbatim:

❯❯❯ lychee --include-verbatim test.md
Issues found in 1 input. Find details below.

[test.md]:
✗ [ERR] github.com/golangci/golangci-lint/cmd/golangci-lint@v1.43.0 | Unreachable mail address: github.com/golangci/golangci-lint/cmd/golangci-lint@v1.43.0: Invalid: Email doesn't exist or is syntactically incorrect

🔍 1 Total ✅ 0 OK 🚫 1 Error (HTTP:1)