fix: Resolve TypeScript errors

Signed-off-by: Hermes Agent <hermes@nosuchhost>

client/node_modules/levelup/lib/promisify.js

@@ -0,0 +1,13 @@
+function promisify () {
+  var callback
+  var promise = new Promise(function (resolve, reject) {
+    callback = function callback (err, value) {
+      if (err) reject(err)
+      else resolve(value)
+    }
+  })
+  callback.promise = promise
+  return callback
+}
+
+module.exports = promisify