doc: add note about tls connection meta data methods

[DaftMonk]

Document current behavior of TLSSocket, as discussed in #3545

[mscdex]

When I first read this, I didn't know what methods were being referred to. You might include an example method (e.g. getPeerCertificate()) or two.

[DaftMonk]

@mscdex Added an example.

[bnoordhuis]

Please wrap at 80 columns. Maybe you can turn getPeerCertificate() into a link?

[DaftMonk]

Updated to use correct column length.

I couldn't get intra-page links working for that section. I tried using the markdown

[getPeerCertificate](#tlssocketgetpeercertificate-detailed-)

and when I opened the preview in github and clicked on it, it didn't work. However typing in the url directly https://github.com/DaftMonk/node/blob/docs-tls-socket/doc/api/tls.markdown#tlssocketgetpeercertificate-detailed- did work.

So I'm not sure what the issue was, but I reverted it back to a code example.

[DaftMonk]

Never mind, I tried again and the link worked this time.

[bnoordhuis]

Thanks, landed in eff8c3e.

[MylesBorins]

landed in v4.x-staging in 8b6120d