Updating version to be inline with other plugins

[Antonio-Laguna]

Hi here @zachleat!

Just seen that 11ty went through a security upgrade before 1.0.0 hits. Tried to update it and npm gave me a hard time since the version outlined here isn't in the range of 0.12.1. I checked other plugins such as syntax-highlighting which was in range so I thought this could be updated so people could easier benefit from this new update.

Let me know if you need any other changes to this.

Thanks!

[zachleat]

Ah sorry I just now saw this and have already published this exact change from #26. I really appreciate the PR though!

https://github.com/11ty/eleventy-plugin-rss/blob/0deac983b2fc960dd5fd50f5cd7d6cf09c67c426/package.json#L36

[Antonio-Laguna]

Awesome!