CloudFormation templates in JSON format

CloudFormation supports both yaml and json formats, but the toolkit only supports yaml.

Although the yaml variation is less verbose (has support for `!Ref` and other shortcuts), many template samples are given in json. Users may be disappointed that they can't work with these templates. Additionally, they may just prefer to use json over yaml.

**Describe the solution you'd like**

Add support for json templates.

**Describe alternatives you've considered**

Users can convert their json templates to yaml. The CloudFormation designer UI lets you easy switch between the formats. But this might be annoying since they might prefer json for its simplicity or uniformity with other config files in their codebases.

Toolkit can detect and offer to convert these templates. This solves the confusion aspect around the inability to run these templates. However, it doesn't help users that prefer sticking with json.

**Additional context**

Looking for feedback from users that encounter / prefer json cfn templates.

Start by locating the toolkit's CloudFormation template handling entry point and checking how YAML templates are currently detected and processed. Define the JSON-template path and verify that representative CloudFormation JSON samples can be used without conversion; the issue names no specific files or tests.

Written by the indexing model from the issue text.