fix: Resolve TypeScript errors

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

client/node_modules/level-errors/test.js

@@ -0,0 +1,20 @@
+var test = require('tape')
+var errors = require('./')
+
+test('all errors are instances of LevelUPError', function (t) {
+  var LevelUPError = errors.LevelUPError
+  var keys = Object.keys(errors)
+
+  keys.forEach(function (key) {
+    t.ok(new errors[key]() instanceof LevelUPError)
+  })
+
+  t.end()
+})
+
+test('NotFoundError has special properties', function (t) {
+  var error = new errors.NotFoundError()
+  t.equal(error.notFound, true)
+  t.equal(error.status, 404)
+  t.end()
+})