Add missing dependency for types

Reviewed-by: Titus Wormer <[email protected]>

Closes GH-9.

Author: Methuselah96

package.json

@@ -30,6 +30,9 @@
     "index.d.ts",
     "index.js"
   ],
+  "dependencies": {
+    "@types/unist": "^2.0.0"
+  },
   "devDependencies": {
     "@types/tape": "^4.0.0",
     "c8": "^7.0.0",