Add support for https://pecl.php.net/

There's about 500 packages there in the [PEAR](https://pear.php.net/) format: https://pecl.php.net/package-stats.php

Not sure if there's an API or if we'll need to scrape html from the website

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Start by examining how this API service supports other package ecosystems, then investigate PECL's package-stats page and whether it exposes an API. Define the metadata that should be imported from the roughly 500 PEAR-format packages and verify that PECL package support works through the service's existing package and version metadata behavior.

Written by the indexing model from the issue text.