Add wiki note about game length limit (#984)

* Add note about game length limit

* Clarify that checkmates on move 300 aren't adjudicated as draws

* Clarify that the 300 moves limit is a lichess-specific behavior

* Fix typos

wiki/Configure-lichess-bot.md

@@ -143,6 +143,8 @@ will precede the `go` command to start thinking with `sd 5`. The other `go_comma
     - `offer_draw_moves`: The absolute value of the evaluation has to be less than or equal to `offer_draw_score` for `offer_draw_moves` amount of moves for the bot to offer/accept draw.
     - `offer_draw_pieces`: The bot only offers/accepts draws if the position has less than or equal to `offer_draw_pieces` pieces.
 
+  Note: If a game reaches 300 moves and no checkmate is delivered on move 300, it is adjudicated as a draw and shows up in the logs as _draw by agreement_ (see [this discussion](https://lichess.org/forum/general-chess-discussion/lichess-300-move-rule-forced-draw) and [this commit](https://github.com/lichess-org/lila/commit/f8921999115878a98431cd722b267281793b7f6f)). That's a lichess-specific behavior which doesn't depend on lichess-bot version or configuration.
+
 ## Options for correspondence games
 - `correspondence` These options control how the engine behaves during correspondence games.
   - `move_time`: How many seconds to think for each move.