github: add a build workflow (#6)

.github/workflows/build.yml

@@ -0,0 +1,21 @@
+---
+name: Build
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: 3.0
+    - name: Install Dependencies
+      run: |
+        gem install test-unit
+        make clean
+    - name: Build and run Tests
+      run: |
+        make all
+        make test

README.md

@@ -1,4 +1,4 @@
-# The Keccak (SHA-3) extension for Ruby
+# The Keccak (SHA-3) digest for Ruby
 
 This Ruby extension implements the SHA-3 ([Keccak](http://keccak.noekeon.org/)) cryptographic hashing algorithm. It is based on the reference C implementation, version 3.2. The exposed interface is almost identical to that of the `digest` standard library.