Fix Envato package dist/download URL (szepeviktor#15)

* Improve PHPDoc types in config

* Check for arrays once in API responses

* Process versions once in package

* Fix Envato package dist/download URL

Resolves szepeviktor#2

When generating the Composer packages for the virtual repository from the configured list of Envato products, this plugin would retrieve the product's download URL via Envato's API and assign it as the package's dist URL. Composer uses this URL as the download's cache key and package URL in a project's `composer.lock` for later installations. Unfortunately, this download URL is signed and expires quickly. This is problematic if ever Composer's cache is cleared or if the project is installed on a different server where Composer's cache is not mirrored.

This is resolved by assigning a more stable versioned dist URL (for the time being, the API request URL to retrieve the download URL) and telling Composer that this plugin needs to update package download URLs before they are downloaded. Then, during the "pre-file-download" event, this plugin will retrieve the download URL from Envato's API while using the stable dist URL as the cache key.

* Improve PHPDoc types and descriptions

* Improve check for download request URL

Ensure the download request URL matches the correct REST URI.

Add support for loading personal token from environment variable or `…

….env` file (szepeviktor#14)

* Add support for loading personal token from environment variable

The config class will look for `ENVATO_TOKEN`.

* Add support for loading personal token from `.env` file

Plugin requires vlucas/phpdotenv v4 or v5.

* Update Installation and Configuration instructions

Changed:
- Added notice that the plugin can be installed locally.
- Improved instructions on configuring the plugin to propose either the local `composer.json` file or the global `config.json` file.
- Added code block hint for environment variable.

* Improve environment variable check in EnvatoConfig

Add support for composer/installers v2 (szepeviktor#12)

Add return types to match newer Composer versions (szepeviktor#10)

* Fixed PHPStan errors in EnvatoAPI.php null checking

* updated return type of the methods in EnvatoPackage class

* Raise min. Composer version

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Co-authored-by: Daniel Taki @DannyTaki 
Co-authored-by: Viktor Szépe <[email protected]>

Fix HTTP options

An example package left in composer.json

Add CompletePackage's isAbandoned method

composer/composer#8638 (comment)

Fix plugin description