Add PHP 8 support

Author: rybakit

Diff for: .github/workflows/qa.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         operating-system: [ubuntu-latest]
-        php-versions: ['7.1', '7.2', '7.3', '7.4']
+        php-versions: ['7.1', '7.2', '7.3', '7.4', '8.0']
     runs-on: ${{ matrix.operating-system }}
     steps:
       - name: Checkout

Diff for: composer.json

@@ -11,7 +11,7 @@
         }
     ],
     "require": {
-        "php": "^7.1",
+        "php": "^7.1|^8",
         "composer/semver": "^1.5",
         "ocramius/package-versions": "^1.4",
         "rybakit/msgpack": "^0.7",
@@ -20,9 +20,9 @@
         "tarantool/client": "^0.8"
     },
     "require-dev": {
-        "php": "^7.1.3",
+        "php": "^7.1.3|^8",
         "friendsofphp/php-cs-fixer": "^2.14",
-        "vimeo/psalm": "^3.9"
+        "vimeo/psalm": "^3.9|^4"
     },
     "autoload": {
         "psr-4": {