JavaScript Doc updates needed

[waderyan]

ping @egamma @mjbvz

Some things that need updating:

• jsconfig.json is not required anymore. We need to figure out the messaging for how to say it isn't required but still recommended. must document when it is required
• We can take out the section about installing typings now that we have ATA.
• We should have a section on ATA that explains reasons why intellisense may not work (for example, one user wanted IntelliSense but they hadn't created a package.json yet).
• Troubleshooting IntelliSense is out of date with ATA.
• Remove references to typings in Q&A.

Some other thoughts.

• Is "Next Generation JavaScript" the right way to describe ES6, ES7, etc.? I haven't seen that vernacular in other places.
• Revisit running babel - I haven't tried this in a while...
• Formatting could use an animation.
• I should look at the common issues list (OneNote table) and add some more Q&A off of what people are running into. Its been a while since I have done that.

[egamma]

@waderyan I've updated the node.js documentation accordingly in this PR #762