Publish preview builds to NPM

[munozemilio]

Is your feature request related to a problem? Please describe.
Myget adds friction to the customer when they want to try new features or available fixes for future releases

Describe the solution you'd like
Have 3 release streams published to NPM:

• RC
• Latest
• Next

Please refer to #864
[enhancement]

[compulim]

❤ this feature! FYI, botframework-directlinejs and botframework-webchat-adapter-ic3 is on this one. botframework-webchat is semi on this one, we publish bundle to GitHub, not NPM yet.

I think every package should have a good version number to aid the devs know how cutting edge they are on:

• Devs can easily know what version they are running
  • This will aid us on supporting bugs: may be the bug has already resolved but the customers are not cutting edge enough. Or maybe the fix doesn't resolve their issues.
• Devs can easily find out if a specific version has a specific PR or not
  • You can look at how Web Chat done this

DLJS and Web Chat use branch and commitish for version number:

• For example, 4.2.0-master.a1b2c3d means 4.2.0 RC built out of master of commitish a1b2c3d
• 👍🏻 It is easy to read where history of time the version is in
• 👍🏻 We could release more than 1 release every day
• 👍🏻 We could set up multiple branches, sometimes, we need a qfe, and sometimes, some customers want a private build accessibility-push to collaborate on something
• 👎🏻 It is not sortable

A mix of both date/sequence and commitish will be great, branch optional.

If you want to use + sign in the version number, be sure to check how escaping works on Windows and Linux, across multiple tools (e.g. npm, lerna, Azure DevOps, Docker, etc).

I don't have experience on GitHub Packages, it may be a good alternative to MyGet for experimental features too.