Adding CI for flysystem v1 (#305)

* Adding CI for flysystem 1

* Split version-bridge.php in two

* Fixed tests and added minimum-stabillity

* Update version of shivammathur/setup-php@1.[0-9].[0-9]

Author: Nyholm

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Set up PHP
-        uses: shivammathur/setup-php@1.7.0
+        uses: shivammathur/setup-php@2.1.2
         with:
           php-version: ${{ matrix.php }}
           coverage: xdebug