fix: upgrade dockerfile-ast from 0.1.0 to 0.2.0

Snyk has created this PR to upgrade dockerfile-ast from 0.1.0 to 0.2.0.

See this package in npm:
https://www.npmjs.com/package/dockerfile-ast

See this project in Snyk:
https://app.snyk.io/org/snyk/project/89596c48-ef89-4c59-b73b-d6d64df7313f?utm_source=github&utm_medium=upgrade-pr

package.json

@@ -33,7 +33,7 @@
     "chalk": "^2.4.2",
     "debug": "^4.1.1",
     "docker-modem": "2.1.3",
-    "dockerfile-ast": "0.1.0",
+    "dockerfile-ast": "0.2.0",
     "elfy": "^1.0.0",
     "event-loop-spinner": "^2.0.0",
     "gunzip-maybe": "^1.4.2",