Add manifest (Level/community#83)

Cherry-picked from Level/leveldown#685.
Closes #144.

Author: vweevers

leveldown.js

@@ -13,7 +13,19 @@ function LevelDOWN (location) {
     throw new Error('constructor requires a location string argument')
   }
 
-  AbstractLevelDOWN.call(this)
+  AbstractLevelDOWN.call(this, {
+    bufferKeys: true,
+    snapshots: true,
+    permanence: true,
+    seek: true,
+    clear: true,
+    createIfMissing: true,
+    errorIfExists: true,
+    additionalMethods: {
+      approximateSize: true,
+      compactRange: true
+    }
+  })
 
   this.location = location
   this.context = binding.db_init()

package.json

@@ -19,7 +19,7 @@
     "prepublishOnly": "npm run dependency-check"
   },
   "dependencies": {
-    "abstract-leveldown": "~6.1.1",
+    "abstract-leveldown": "~6.2.2",
     "napi-macros": "~2.0.0",
     "node-gyp-build": "~4.1.0"
   },