feat: docker-plugin bump

Improved Dockerfile parsing:
- Resolve aliases names on multi-stage builds
- Resolve variables on packages install commands

package.json

@@ -70,7 +70,7 @@
     "proxy-from-env": "^1.0.0",
     "semver": "^6.0.0",
     "snyk-config": "^2.2.1",
-    "snyk-docker-plugin": "1.25.1",
+    "snyk-docker-plugin": "1.29.1",
     "snyk-go-plugin": "1.11.0",
     "snyk-gradle-plugin": "^3.0.2",
     "snyk-module": "1.9.1",