Ability to add presets for plugins not currently listed

[RustoMCSpit]

There should be a toggle which lets you manually input the name of the author and the name of the plugin. This would allow you to upload presets for plugins not currently listed. This should also apply to plugins within projects.

[kmturley]

This warrants a discussion. If the plugin is not supported by the registry, how do we tie an identifier to it. Need to think about it more.

The plugin identifier comprises of: org-name/plugin-name. So maybe the form could ask for those values and then generate the identifier automatically

[RustoMCSpit]

pretty much, but that would be more manual work for us to validate that they used the correct form