implement loops/list comprehension

[Alex Frankel]

spec: https://github.com/Azure/bicep/blob/master/docs/spec/loops.md

[David Gard]

@alex-frankel This feature and conditions (#186) sound very exciting. Is there an estimated completion date for the v0.3 milestone?

[Alex Frankel]

0.3 is sometime in Jan/Feb, but loops and conditions will probably be released earlier as a 0.2.* release to make sure it is working as expected