Add version tags and publish which version is supported by each pelican version

[oldherl]

For some reasons, not everyone is using the latest pelican version. It would help those users if such a table is published with the latest read-more version is supported by each pelican version. E.g., read-more X.X is the last version supported by pelican 4.8.0 and read-more Y.Y is the last version supported by pelican 4.9.0.

[avaris]

What do you mean? Only one version of this plugin is published.