Snippet support for tasks.json

[dbaeumer]

Details

Instead of generating a tasks.json with a lot of well know tasks.json examples we now present the user a list of snippets to choose from. To test do the following:

• new workspace
• F1 > Task Configure > Enter

Expected: the editor opens and it looks like this:

You can pick a snippet and it gets correctly inserted into the task.json

[felixfbecker]

can extensions provide new snippets for tasks.json? For example, a Java language support extension might want to provide a build task with javac and a problem matcher.

[egamma]

@felixfbecker not yet, pls see #3125

[dbaeumer]

Reopen to retest in March

[felixfbecker]

Please consider to also add a snippet for npm scripts, many people use them.

[dbaeumer]

Closing in favour of #4019.
Created #4115 for the npm request.