Allow installing on PHP 8

.github/CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing
+
+First of all, **thank you** for contributing!
+
+Here are a few rules to follow in order to ease code reviews and merging:
+
+- follow the coding standard of the project
+- run the test suite
+- write (or update) tests when applicable
+- write documentation for new features
+- use [commit messages that make sense](http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html)
+
+When creating your pull request on GitHub, please write a description which gives the context and/or explains why you are creating it.

.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: mnapoli # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']

.github/pull_request_template.md

@@ -0,0 +1,5 @@
+<!--
+Please explain the motivation behind the changes.
+
+In other words, explain **WHY** instead of **WHAT**.
+-->

.github/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: CI
+
+on:
+    push:
+        branches: ['master']
+    pull_request:
+        branches: ['*']
+    schedule:
+        -   cron: '0 0 * * *'
+
+jobs:
+
+    tests:
+        name: Tests - PHP ${{ matrix.php }} ${{ matrix.dependency-version }}
+        runs-on: ubuntu-latest
+        timeout-minutes: 15
+        strategy:
+            matrix:
+                php: [ '7.3', '7.4', '8.0' ]
+                dependency-version: [ '' ]
+                include:
+                    -   php: '7.3'
+                        dependency-version: '--prefer-lowest'
+        steps:
+            -   name: Checkout
+                uses: actions/checkout@v2
+            -   name: Setup PHP
+                uses: shivammathur/setup-php@v2
+                with:
+                    php-version: ${{ matrix.php }}
+                    tools: composer:v2
+                    coverage: none
+            -   name: Cache Composer dependencies
+                uses: actions/cache@v2
+                with:
+                    path: ~/.composer/cache
+                    key: php-${{ matrix.php }}-composer-locked-${{ hashFiles('composer.lock') }}
+                    restore-keys: php-${{ matrix.php }}-composer-locked-
+            -   name: Install PHP dependencies
+                run: composer update ${{ matrix.dependency-version }} --prefer-dist --no-interaction --no-progress --no-suggest
+            -   name: PHPUnit
+                run: vendor/bin/phpunit

composer.json

@@ -16,7 +16,7 @@
         }
     },
     "require": {
-        "php": "^7.3",
+        "php": ">=7.3",
         "phpunit/phpunit": "^8.5|^9.0"
     }
 }