Fix types by moving some dev-dependencies to dependencies

Closes GH-2.

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>
Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Author: remcohaszing

package.json

@@ -39,14 +39,14 @@
   ],
   "dependencies": {
     "@types/estree-jsx": "^0.0.1",
-    "@types/mdast": "^3.0.0"
+    "@types/mdast": "^3.0.0",
+    "mdast-util-from-markdown": "^1.0.0",
+    "mdast-util-to-markdown": "^1.0.0"
   },
   "devDependencies": {
     "@types/tape": "^4.0.0",
     "acorn": "^8.0.0",
     "c8": "^7.0.0",
-    "mdast-util-from-markdown": "^1.0.0",
-    "mdast-util-to-markdown": "^1.0.0",
     "micromark-extension-mdxjs-esm": "^1.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",