Make npm audit happy (#50)

* Upgrade "ansi-regex" 5.0.0 => 5.0.1

And various other stuff because npm can't just upgrade one thing in the
lockfile, it need to upgrade everything it can. Move along, nothing
interesting to see here.

* Upgrade "eslint" 6 => 7

And also unpin the minor version. This resolves a bunch of "critical"
audit advisories from transitive dependencies.

package.json

@@ -30,6 +30,6 @@
     "@actions/core": "^1.2"
   },
   "devDependencies": {
-    "eslint": "^6.8.0"
+    "eslint": "^7"
   }
 }