Add GHA to check Tests

.github/workflows/test.yml

@@ -0,0 +1,13 @@
+name: Test
+on: [push, pull_request]
+env:
+  CARGO_TERM_COLOR: always
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build
+      run: cargo build --verbose
+    - name: Run tests
+      run: cargo test --verbose

README.md

@@ -1,4 +1,4 @@
-# fft-rs
+# fft-rs [![Test](https://github.com/arnaucube/fft-rs/workflows/Test/badge.svg)](https://github.com/arnaucube/fft-rs/actions?query=workflow%3ATest)
 
 Fast Fourier Transform implementation in Rust.