Add Tests badge to readme

.github/workflows/php.yml

@@ -12,14 +12,14 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Validate composer.json and composer.lock
         run: composer validate --strict
 
       - name: Cache Composer packages
         id: composer-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: vendor
           key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}

README.md

@@ -6,6 +6,8 @@ With this query builder you can build queries for Flux. Flux is a powerful open
 [![License](http://poser.pugx.org/arendsen/fluxquerybuilder/license)](https://packagist.org/packages/arendsen/fluxquerybuilder) 
 [![PHP Version Require](http://poser.pugx.org/arendsen/fluxquerybuilder/require/php)](https://packagist.org/packages/arendsen/fluxquerybuilder)
 
+[![Tests](https://github.com/davidarendsen/fluxquerybuilder/actions/workflows/php.yml/badge.svg)](https://github.com/davidarendsen/fluxquerybuilder/actions/workflows/php.yml)
+
 ## Documentation 
 The documentation of this project is available in the [docs folder](docs/00-index.md).