Subsections do not expand when linked from a section

[akegaviar]

1. Open a section in docs
2. Click a link that leads to a subsection
3. The subsection does not expand by default, which leads to confusion

Example:

1. Click any link from the See also section at https://docs.dev.chainstack.com/blockchains/
2. The subsection page opens but the user is still in the Blockchains section

[akegaviar]

Back to backlog until this gets implemented vuejs/vuepress#1497