fix the readme link

Author: 38

README.md

@@ -136,7 +136,7 @@ To view the source code for each example, please click on the example image.
   * [Plotting on HTML5 canvas with WASM Backend](#plotting-on-html5-canvas-with-wasm-backend)
   * [What types of figure are supported?](#what-types-of-figure-are-supported)
   * [Concepts by examples](#concepts-by-examples)
-    + [Drawing Back-ends](#drawing-backends)
+    + [Drawing Back-ends](#drawing-back-ends)
     + [Drawing Area](#drawing-area)
     + [Elements](#elements)
     + [Composable Elements](#composable-elements)

doc-template/gen-toc.sh

@@ -9,7 +9,7 @@ BEGIN {
 }
 {
 	link=tolower($2)
-	gsub(/[^a-z0-9 ]/, "", link);
+	gsub(/[^a-z0-9 \-]/, "", link);
 	gsub(/[^a-z0-9]/, "-", link);
 	print "  "level[$1]"["$2"](#"link")"
 }'

src/lib.rs

@@ -269,7 +269,7 @@ including bitmap, vector graph, piston window, GTK/Cairo and WebAssembly.
   * [Plotting on HTML5 canvas with WASM Backend](#plotting-on-html5-canvas-with-wasm-backend)
   * [What types of figure are supported?](#what-types-of-figure-are-supported)
   * [Concepts by examples](#concepts-by-examples)
-    + [Drawing Back-ends](#drawing-backends)
+    + [Drawing Back-ends](#drawing-back-ends)
     + [Drawing Area](#drawing-area)
     + [Elements](#elements)
     + [Composable Elements](#composable-elements)