docs: Fill in the documentation index and re-build the texinfo.

Author: szermatt

docs/source/index.rst

@@ -1,7 +1,37 @@
 Turtles
 =======
 
-TODO
+Turtles is an Emacs elisp package that helps write ERT-based tests
+that check how Emacs renders buffers and windows. The ERT tests can be
+run interactively or in batch mode. You'll find the source code of
+this package on https://github.com/szermatt/turtles
+
+Go to :ref:`tut` to get started.
+
+Turtles is especially suited to test:
+
+- the effect of display, before-string, after-string text properties
+
+- the effect of overlays
+
+- text visibility
+
+- mode lines
+
+- complex minibuffer interactions
+
+*This program is free software: you can redistribute it and/or
+modify it under the terms of the GNU General Public License as
+published by the Free Software Foundation; either version 3 of the
+License, or (at your option) any later version.*
+
+*This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.*
+
+*You should have received a copy of the GNU General Public License
+along with this program.  If not, see* http://www.gnu.org/licenses/
 
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