Add Laravel 9 support

[gbuckingham89]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Tests pass?	✔️
Fixed issues	comma-separated list of tickets # fixed by the PR, if any

This PR simply adds support for Laravel 9 (released today).

[J-Brk]

@emtudo Isn't it too fast to already merge this PR? Have we done tests to confirm the package actually works well under Laravel 9? Do we need to add unit tests? How about the documentation?

[emtudo]

Laravel 9 is basically version 8. The structure hasn't changed, if it works on version 8, it has to work on version 9.

[sawirricardo]

composer not yet updated?

Using version ^0.21.0 for artesaos/seotools
./composer.json has been updated
Running composer update artesaos/seotools
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires artesaos/seotools ^0.21.0 -> satisfiable by artesaos/seotools[v0.21.0].
    - artesaos/seotools v0.21.0 requires illuminate/config 5.8.* || ^6.0 || ^7.0 || ^8.0 -> found illuminate/config[v5.8.0, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev, v8.0.0, ..., 8.x-dev] but these were not loaded, likely because it conflicts with another require.

You can also try re-running composer require with an explicit version constraint, e.g. "composer require artesaos/seotools:*" to figure out if any version is installable, or "composer require artesaos/seotools:^2.1" if you know which you need.

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

[emtudo]

A version tag has not yet been created.

[emtudo]

Added tag.