Add GitHub action to run test suite

.github/main.workflow

@@ -0,0 +1,8 @@
+workflow "test" {
+  resolves = ["CI Test Runner"]
+  on = "push"
+}
+
+action "CI Test Runner" {
+  uses = "./.github/test_runner"
+}

.github/test_runner/Dockerfile

@@ -0,0 +1,14 @@
+FROM ruby:2.6.2
+
+LABEL "com.github.actions.name"="CI Test Runner"
+LABEL "com.github.actions.description"="Run the full test suite"
+LABEL "com.github.actions.icon"="gear"
+LABEL "com.github.actions.color"="purple"
+
+ENV LC_ALL C.UTF-8
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US.UTF-8
+
+COPY entrypoint.sh /
+
+ENTRYPOINT ["/entrypoint.sh"]

.github/test_runner/entrypoint.sh

@@ -0,0 +1,3 @@
+#!/bin/sh -l
+
+script/cibuild