Change installer type to `phpcodesniffer-standard`

Created by: Potherca

Problem/Motivation

This composer plugin uses php-codesniffer-standards as package type for custom codesniff packages to use.

Some other projects that offer similar functionality (for instance SimplyAdmire/ComposerPlugins and DealerDirect/phpcodesniffer-composer-installer use phpcodesniffer-standard (without the hyphen - between php and codesniffer.

There are also a lot of packages that adhere to this type.

Proposed changes

It could be beneficial for the adaptation rate of all of such projects to all use the same type.

I would suggest changing the type to phpcodesniffer-standard before the first stable release.