[JS] Add details to README in certificate samples

[JhontSouth]

#minor

Description

This PR adds more information to the README certificate samples to have an easier complete guide for SSL/TLS certificate configuration.

Proposed Changes

• Updated Readme of node js samples 84.bot-authentication-certificate and 85.bot-authentication-sni.

[sw-joelmut]

Similar changes made for .NET could be made here #429.
Also, the linked images are not showing up in the readme.

[andres-robinet-sw]

Check casing of links.
If repo is cloned in linux/unix system, then Images is not the same as images.

[JhontSouth]

Similar changes made for .NET could be made here #429. Also, the linked images are not showing up in the readme.

Changes applied

[sw-joelmut]

I noticed we dont have the MicrosoftAppTenantId and MicrosoftAppType, whe should include them here in the .env and the index.js, because they could be used with this flow path.

[JhontSouth]

https://github.com/microsoft/botbuilder-js/blob/066b405a8630e4f6c7d165ef939982181f6bbc6a/libraries/botbuilder-core/src/configurationBotFrameworkAuthentication.ts#L28

MicrosoftAppType doesn't exist in ConfigurationBotFrameworkAuthenticationOptions

[JhontSouth]

Also does not exist in CertificateServiceClientCredentialsFactory(SN+I)
https://github.com/microsoft/botbuilder-js/blob/066b405a8630e4f6c7d165ef939982181f6bbc6a/libraries/botframework-connector/src/auth/certificateServiceClientCredentialsFactory.ts#L41

[JhontSouth]

added Tenant Id

[sw-joelmut]

The app type should be added as well, i know its not in the ConfigurationBotFrameworkAuthenticationOptions, but it is in the https://github.com/microsoft/botbuilder-js/blob/066b405a8630e4f6c7d165ef939982181f6bbc6a/libraries/botbuilder-core/src/configurationServiceClientCredentialFactory.ts which is the one that instantiates the CertificateServiceClientCredentialsFactory

[JhontSouth]

Promoted /3994