feature request: document support multiple version

[Anilople]

Is your feature request related to a problem? Please describe. When user view the document https://www.apolloconfig.com/ , user may be only care about the document match their apollo's version.

For example, when user user's apollo version is 1.5.0, he/she may be confuse when see the feature above 1.5.0

Describe the solution you'd like When someone use elasticsearch, its official site https://www.elastic.co/guide/en/elasticsearch/reference/7.17/index.html support choose the matched version of document.

Maybe we can add a button version on the top right of site? and jump to that version's document which mark by the git tag.

Additional context It's will improve the experience about the document, decrease the user's confuse.

[nobodyiam]

Good idea! I suppose this will also make the documentation more precise and simple, e.g. we don't need to mark this section is for 2.0.0+, this section is for 1.9.0+, etc.