Add default value for fromEnd and toEnd.

spec/1.0.md

@@ -72,7 +72,7 @@ Edges are lines that connect one node to another.
   - `right`
   - `bottom`
   - `left`
-- `fromEnd` (optional, string) is the shape of the endpoint at the edge start. Valid values:
+- `fromEnd` (optional, string) is the shape of the endpoint at the edge start. Defaults to `none` if not specified. Valid values:
   - `none`
   - `arrow`
 - `toNode` (required, string) is the node `id` where the connection ends.
@@ -81,7 +81,7 @@ Edges are lines that connect one node to another.
   - `right`
   - `bottom`
   - `left`
-- `toEnd`  (optional, string) is the shape of the endpoint at the edge end. Valid values:
+- `toEnd`  (optional, string) is the shape of the endpoint at the edge end. Defaults to `arrow` if not specified. Valid values:
   - `none`
   - `arrow`
 - `color` (optional, `canvasColor`) is the color of the line, see the Color section.
@@ -99,4 +99,4 @@ The `canvasColor` type is used to encode color data for nodes and edges. Colors
 - `"5"` cyan
 - `"6"` purple
 
-Specific values for the preset colors are intentionally not defined so that applications can tailor the presets to their specific brand colors or color scheme.
+Specific values for the preset colors are intentionally not defined so that applications can tailor the presets to their specific brand colors or color scheme.