Removed composer.lock, set GH action to test against 7.3, 7.4 & 8.0

.github/workflows/php.yml

@@ -9,12 +9,16 @@ on:
 jobs:
   build:
     
+    strategy:
+      matrix:
+        php: ['7.3', '7.4', '8.0']
+
     runs-on: ubuntu-latest
 
     steps:
     - uses: shivammathur/setup-php@2.11.0
       with:
-        php-version: '7.4'
+        php-version: ${{ matrix.php }}
         extensions: 'xdebug'
 
     - uses: actions/checkout@v2

.gitignore

@@ -1,5 +1,6 @@
 .DS_Store
 vendor
+composer.lock
 tests/tmp/*
 phpDocumentor.phar
 phpdoc.xml