Add game 'life' api reference (#1569)

docs/reference/game/add-life.md

@@ -0,0 +1,33 @@
+# add Life
+
+Increase the number of lives remaining by some amount.
+
+```sig
+game.addLife(0)
+```
+
+The life count in the game is increased by the number of lives you say.
+
+## Parameters
+
+* **life**: a [number](/types/number) to remove from the count.
+
+## Example #example
+
+Add `20` more lives to the life count if the player's score reaches `10000` points.
+
+```blocks
+let giveLives = true
+
+if (game.score() > 9999) {
+    if (giveLives) {
+        game.addLife(20)
+        giveLives = false
+    }
+}
+```
+
+## See also #seealso
+
+[set life](/reference/game/set-life),
+[remove life](/reference/game/remove-life)