Improve /opening's handling of transpositions

[superuser-does]

Background

Chess openings (/opening) permits users to navigate by:

1. Clicking through moves in a specific sequence to reach a certain positions in the default Opening pages view, or
2. Navigating to positions directly through the alternate Name tree view, or
3. Inputting a move sequence in the search box.

Issue

When users reach a specific position, the page may lack content from another page, even when the position is identical.
This is almost always because it is a less-popular transposition into another opening.

Also, some - maybe all positions, cannot be reached via transposition when entering the exact sequence in the search box.

Example:

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 works for reaching the main main Four Knights game page. It is the most common way to reach this position.

Changing even one of these moves in that sequence will no longer link to that page.

If the same position were reached through 1. Nc3 e5 2. Nf3 Nc6 3. e4 Nf6 the user would get a Four Knights Game page without the description.

It is also not possible to reach this page by entering this move sequence in the search box.

[Siderite]

In LiChess Tools you get something like this for Wiki URLs in Analysis Board. The tool calculates the moves for all Wikibooks chess entries and determines the position for each, then searches the URL by FEN. I had no experience with /opening and I didn't know Wiki links were used there, too. I implemented it for v2.4.35

But you're right, it should be native. I would extend the same attention to Explorer, which has a link to the opening, but regardless which combination of moves you use, it never gets to the more specific /opening URL than its name.