change BNF (but not implementation of BNF) for parsing, to handle layers, and also change minimum key in layer tree to be 1

fcore/parser/parser.md

@@ -4,14 +4,16 @@ The parsing functionality is for saving and loading from a custom file format.
 
 The BNF for the custom file format is below.
 
-Terminals are surrounded by `**` to the left and right. (rule)+ means "1 o more".
+Terminals are surrounded by `**` to the left and right. (rule)+ means "1 or more".
 
 ```
 int ::= (0-9)+
 
 item ::= **{** int int int int int int int int **}**
 
-grid ::= int int **{** (item)+ **}**
+grid ::= **[** item **]**
+
+grid_list ::= int int **{** (grid)+ **}**
 ```
 
 The first two `int`s in the grid `int int **{** (item)+ **}**` always follow the order: `canvasWidth canvasHeight`.