Add TravisCI config file

Author: hacknug

Diff for: .travis.yml

@@ -0,0 +1,16 @@
+language: node_js
+node_js:
+  - "8"
+  - "10"
+  - "12"
+
+cache:
+  directories:
+    - node_modules
+
+before_install:
+  - curl -L https://unpkg.com/@pnpm/self-installer | node
+
+script:
+  - pnpm install
+  - pnpm run test