Offer .sarif and .sarif-external-properties file templates

[ghost]

Add options to File, New:

.sarif file, with initial contents

{
  "$schema": "https://raw.githubusercontent.com/oasis-tcs/sarif-spec/master/Schemata/sarif-schema-2.1.0.json",
  "version": "2.1.0",
  "runs": [
    {
      "tool": {
        "driver": {
          "name": "Tool Name"
        }
      },
      "results": [
      ]
    }
  ]
}

.sarif-external-properties file, with initial contents

{
  "$schema": "https://raw.githubusercontent.com/oasis-tcs/sarif-spec/master/Schemata/sarif-external-property-file-schema-2.1.0.json",
  "version": "2.1.0"

}

[ghost]

@michaelcfanning FYI