fix: Resolve TypeScript errors

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

client/node_modules/abstract-leveldown/test/util.js

@@ -0,0 +1,10 @@
+var nfre = /NotFound/i
+
+exports.verifyNotFoundError = function verifyNotFoundError (err) {
+  return nfre.test(err.message) || nfre.test(err.name)
+}
+
+exports.isTypedArray = function isTypedArray (value) {
+  return (typeof ArrayBuffer !== 'undefined' && value instanceof ArrayBuffer) ||
+    (typeof Uint8Array !== 'undefined' && value instanceof Uint8Array)
+}