README: link tool screencasts

README.md

@@ -150,7 +150,11 @@ distributed with this program for an example. An overview on the syntax:
     # Comments can be either # Shell-Style or
     /* C-Style. */
 
-This entry defines the tool `red Pen`, a pen with size 7 and color red.
+The `PEN`-tool is for freehand drawing.
+
+![PEN tool](data/tool-pen.webp)
+
+The following entry defines the tool `red Pen`, a pen with size 7 and color red.
 You can specify an RGB color in X-Style: e.g. `#FF0033`, specify an
 RGBA color like so: `rgba(0, 0, 255, 0.6)` or use color names from
 [`rgb.txt`](https://en.wikipedia.org/wiki/X11_color_names).
@@ -198,10 +202,14 @@ the shape. Try it out to see the effect.
 
 A `LINE`-tool draws straight lines.
 
+![LINE tool](data/tool-line.webp)
+
     "green Line" = LINE (color = "green");
 
 A `RECT`-tool draws rectangles.
 
+![RECT tool](data/tool-rect.webp)
+
     "red Rectangle" = RECT (color = "red");
 
 A `SMOOTH`-tool that behaves like `PEN` except that it produces smoothed curves.
@@ -211,6 +219,8 @@ within which intermediate points are "simplified away". Closed paths
 can be drawn using the `snap=N` option where `N` indicates the maximum 
 distance between start and end point within which these "snap" together. 
 
+![SMOOTH tool](data/tool-smooth.webp)
+
     "smoothed line" = SMOOTH (color = "red" simplify=10 snap=30);
 
 A `ORTHOGONAL`-tool that behaves like `SMOOTH` except that it produces
@@ -220,6 +230,8 @@ and vertical direction when their direction deviated by a maximum of
 arcs with a certain `radius`, if these segments exceed a length of
 `minlen`.
 
+![ORTHOGONAL tool](data/tool-orthogonal.webp)
+
     "ortho line" = ORTHOGONAL (color="red" size=5 simplify=15 radius=20 minlen=50 snap=40);
 
 If you define a tool with the same name as an input-device