Documented the /extract command

docs/extract.md

@@ -0,0 +1,42 @@
+# /extract
+
+Extracts knowledge from a game by using the Steinitz evaluation.
+
+## `variant`
+
+The chess variant as per these options.
+
+- `classical` chess, also known as standard or slow chess.
+- `960` is the same as classical chess except that the starting position of the pieces is randomized.
+- `dunsany` is an asymmetric variant in which Black has the standard chess army and White has 32 pawns.
+- `losing` chess, the objective of each player is to lose all of their pieces or be stalemated.
+- `racing-kings` consists of being the first player to move their king to the eighth row.
+- `capablanca` incorporates two new pieces, the archbishop and the chancellor, and is played on a 10×8 board.
+- `capablanca-fischer` is a mix of Capablanca chess and Chess960.
+
+## `movetext`
+
+The sequence of moves played in the game.
+
+---
+
+### Usage
+
+#### Example
+
+```js
+ws.send('/extract "{\"variant\":\"classical\",\"movetext\":\"1.e4 e5 2.Nf3 Nc6 3.Bc4\"}"');
+```
+
+```text
+{
+  "/extract": [
+    0,
+    0.5,
+    0,
+    1,
+    0.25,
+    1
+  ]
+}
+```

mkdocs.yml

@@ -24,6 +24,7 @@ nav:
       - /takeback: takeback.md
     - Parameterized:
       - /accept: accept.md
+      - /extract: extract.md
       - /heuristic: heuristic.md
       - /leave: leave.md
       - /legal: legal.md