Update dependencies for PHP 8

Author: DiegoPino

composer.json

@@ -3,16 +3,17 @@
     "description": "A utility library for working with Data Packages",
     "license": "MIT",
     "require": {
-        "php": ">=7.1",
-        "ext-zip": "*",
-        "justinrainbow/json-schema": "^5.2",
-        "frictionlessdata/tableschema": "^v1.0.0"
+        "php": ">=8",
+        "justinrainbow/json-schema": "^5.3 || ^6.6",
+        "frictionlessdata/tableschema": "^v1",
+        "ext-json": "*",
+        "ext-zip": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.5.20",
-        "satooshi/php-coveralls": "^1.0",
+        "phpunit/phpunit": ">=7.5 <10.0",
+        "php-coveralls/php-coveralls": "^2.4",
         "psy/psysh": "@stable",
-        "squizlabs/php_codesniffer": "^3.5"
+        "squizlabs/php_codesniffer": "^3.7"
     },
     "autoload": {
         "psr-4": {