Prepare support for PHP 8

Author: janbarasek

.github/workflows/coding-style.yml

@@ -10,7 +10,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: shivammathur/setup-php@v2
         with:
-          php-version: 7.4
+          php-version: 8.0
           coverage: none
 
       - run: composer create-project nette/code-checker temp/code-checker ^3 --no-progress

.github/workflows/main.yml

@@ -19,12 +19,12 @@ jobs:
     - name: Install PHP
       uses: shivammathur/setup-php@master
       with:
-        php-version: 7.4
+        php-version: 8.0
 
     - name: Install composer deps
       run: |
         composer create-project nette/code-checker temp/code-checker ^3 --no-progress
-        composer create-project nette/coding-standard temp/coding-standard ^2 --no-progress
+        composer create-project nette/coding-standard temp/coding-standard ^3 --no-progress
 
         # Install app deps
         composer install --no-interaction --prefer-dist

composer.json

@@ -17,9 +17,9 @@
 		"ext-dom": "*"
 	},
 	"require-dev": {
-		"phpstan/phpstan": "^0.12.18",
-		"tracy/tracy": "^2.7",
-		"phpstan/phpstan-nette": "^0.12.6",
+		"phpstan/phpstan": "^0.12.74",
+		"tracy/tracy": "^2.8",
+		"phpstan/phpstan-nette": "^0.12.14",
 		"roave/security-advisories": "dev-master"
 	},
 	"autoload": {