docs: Adding tls document describing what we support

[jebrando]

Checklist

• I have read the [contribution guidelines] (https://github.com/Azure/azure-iot-sdk-node/blob/master/.github/CONTRIBUTING.md).
• I added or modified the existing tests to cover the change (we do not allow our test coverage to go down).
• If this is a modification that impacts the behavior of a public API
  • I edited the corresponding document in the devdoc folder and added or modified requirements.

Reference/Link to the issue solved with this PR (if any)

Description of the problem

Description of the solution

[anthonyvercolano]

[ericmitt]

typo: should be connection
#Resolved

[ericmitt]

How a customer can force node to use tls1.2 ? Is it possible at 'node runtime' level like Java, or node just use what the OS provide? The doc should explain that. #Resolved

[jebrando]

This can not be done without a code change to the underlying TLS library. So we are submitting a PR to the MQTT library that we're using.

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In reply to: 572325484 [](ancestors = 572325484)