Update FlowChart (#1377)

docs/Developer.md

@@ -1,17 +1,20 @@
 
-## Flow chart
+## Developer
 
-![FlowChart](drawio/FlowChart.svg)
+### Flow chart
 
+![FlowChart](drawio/FlowChart.svg)
 
+### Edit flow chart
 - Use [drawio](https://app.diagrams.net/) to edit.
 
 1. Open [drawio](https://app.diagrams.net/) in brower
 2. Menu → File → Open from ... → Device:
 
-Select [FlowChart.html](FlowChart.html)
+   Select [FlowChart.html](drawio/FlowChart.html)
 
 3. Edit flow chart
 4. Export to svg:
 
-Menu → File → Export as... → SVG...
+   Menu → File → Export as... → SVG...
+