Update installation instructions for composer

[mattjric]

Description

When installing the Auth0 plugin on the latest version of WordPress 6.5.3 the following changes to the README.md were required. I have searched open and closed issues and not found this issue - I am raising this draft pull request ahead of raising an issue.

1. Included a message stating the version if this plugin found on the WordPress plugins directory is not compatible with newer versions of WordPress (I don't know exactly what version this incompatibility starts, I am on WordPress 6.5.3). Is there an ETA for the public version of this plugin to be updated?

2. Added an instruction top copy the contents of ./vendor/auth0/wordpress/ to './auth0/' after running composer - necessary on WordPress 6.5.3 otherwise the plugin does not appear on the plugins list in /wp-admin/plugins.php

[ec2-user@ip-xxx plugins]$ ll
-rw-r--r--.  1 ec2-user ec2-user   230 May  8 11:14 composer.json
-rw-r--r--.  1 ec2-user ec2-user 65786 May  8 11:14 composer.lock
-rw-rw-r--.  1 apache   apache      28 Jun  5  2014 index.php
drwxr-xr-x.  9 ec2-user ec2-user   132 May  8 11:19 vendor
...
[ec2-user@ip-xxx plugins]$ ll vendor/
drwxr-xr-x. 4 ec2-user ec2-user    40 May  8 11:14 auth0
-rw-r--r--. 1 ec2-user ec2-user   771 May  8 11:14 autoload.php
drwxr-xr-x. 3 ec2-user ec2-user 16384 May  8 11:14 composer
drwxr-xr-x. 3 ec2-user ec2-user    18 May  8 11:14 nyholm
drwxr-xr-x. 4 ec2-user ec2-user    55 May  8 11:14 php-http
drwxr-xr-x. 9 ec2-user ec2-user   130 May  8 11:14 psr
drwxr-xr-x. 9 ec2-user ec2-user 16384 May  8 11:14 psr-discovery
drwxr-xr-x. 6 ec2-user ec2-user   108 May  8 11:14 symfony
[ec2-user@ip-xxx plugins]$ ll vendor/auth0/
total 16
drwxr-xr-x. 3 ec2-user ec2-user    89 Jan 11 15:28 auth0-php
drwxr-xr-x. 4 ec2-user ec2-user 16384 Dec 12 19:14 wordpress
[ec2-user@ip-xxx plugins]$ ll vendor/auth0/wordpress/
total 80
-rw-r--r--. 1 ec2-user ec2-user  2319 Dec 12 19:14 CHANGELOG.md
-rw-r--r--. 1 ec2-user ec2-user  1118 Dec 12 19:14 LICENSE.md
-rw-r--r--. 1 ec2-user ec2-user 14228 Dec 12 19:14 README.md
-rw-r--r--. 1 ec2-user ec2-user  3754 Dec 12 19:14 composer.json
-rw-r--r--. 1 ec2-user ec2-user    52 Dec 12 19:14 opslevel.yml
-rw-r--r--. 1 ec2-user ec2-user   575 Dec 12 19:14 phpstan.neon.dist
-rw-r--r--. 1 ec2-user ec2-user   757 Dec 12 19:14 phpunit.xml.dist
-rw-r--r--. 1 ec2-user ec2-user   973 Dec 12 19:14 psalm.xml.dist
-rw-r--r--. 1 ec2-user ec2-user   800 Dec 12 19:14 public-signing-key.pub
-rw-r--r--. 1 ec2-user ec2-user 27967 Dec 12 19:14 rector.php
drwxr-xr-x. 7 ec2-user ec2-user   133 Dec 12 19:14 src
-rw-r--r--. 1 ec2-user ec2-user  2772 Dec 12 19:14 wpAuth0.php

Testing

Manually tested in my environment

Checklist

• [N/A] I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• [Y] The correct base branch is being used, if not the default branch