fix: Resolve TypeScript errors

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

client/node_modules/abstract-leveldown/.travis.yml

@@ -0,0 +1,28 @@
+sudo: false
+language: node_js
+
+matrix:
+  fast_finish: true
+  include:
+  - node_js: 6
+    env: CMD=test
+  - node_js: 8
+    env: CMD=test
+  - node_js: 10
+    env: CMD=test
+  - node_js: stable
+    env: CMD=test-browsers
+    addons:
+      sauce_connect: true
+      hosts:
+        - airtap.local
+
+before_script: git fetch --tags
+
+script:
+  - DEBUG=airtap:* npm run $CMD
+
+after_success: npm run coverage
+
+notifications:
+  email: false