[Docs] handle version in docs

[kavilla]

Is your feature request related to a problem? Please describe.

The docs site is versioned based on off major and minor version, for example: https://opensearch.org/docs/1.0/dashboards/index/.

Describe the solution you'd like

This service: https://github.com/opensearch-project/OpenSearch-Dashboards/blob/main/src/core/public/doc_links/doc_links_service.ts will have to be updated to take the branch version (or if main latest) then route the right page. We also need to start making sure to update https://github.com/opensearch-project/OpenSearch-Dashboards/blob/main/package.json#L15 to be the correct version so if on the 1.2 branch then this line should read 1.2

Describe alternatives you've considered

n/a

Additional context

Blocking: #769