**Background**
The CommunityRequests extension is currently designed to store votes as wikitext on a `/Votes` subpage of either a focus area, and later wishes. When a vote is saved, we need to update `communityrequests_wishes.cr_vote_count` (wishes) or `communityrequests_focus_areas.crfa_vote_count` (focus areas) accordingly.
**Acceptance criteria**
* Add a configuration variable to specify what the voting subpage is called. i.e. `$wgCommunityRequestsVotingSubpage = '/Voting';`
* Introduce a parser tag for votes. We don't store any voting data other than the tally count, so an empty parser function with no output is fine for now, i.e. `<vote>`. This will get embedded in the [[ https://meta.wikimedia.org/wiki/Template:Community_Wishlist/Support | voting template ]], so don't worry about presentation.
* Keep a tally of each vote, storing the counter with `ParserOutput::setExtensionData()`, similar to what we're doing for the other parser tags
* Use the [[ https://www.mediawiki.org/wiki/Manual:Hooks/LinksUpdateComplete | LinksUpdateComplete ]] hook to get the final count (pulling the tally from the extension data)
* Before saving, ensure we're on a qualifying page using the new config variable and other config variables like `CommunityRequestsWishPagePath` and `CommunityRequestsWishIdPrefix` (equivalents for focus areas should also exist)
* Get the Wish or FocusArea object from the page title, and update the vote count field for the corresponding row in the wishes/focus_areas table