index.ipynb: Add table of contents (of notebooks)

Note that this table of contents is currently generated by hand, and it
uses titles and not names of notebooks.

NOTE: README.md was updated manually.

Author: jnareb

README.md

@@ -44,6 +44,16 @@ Such operations include:
 
 Only the first command performs straight reachability query.
 
+## Table of contents
+
+> Warning: this is not generated automatically
+
+1. [Graphs in Python](01_tools.ipynb)
+2. [Related works: various reachability labelings](02_related.ipynb)
+3. [Example directed graphs](03_example_graphs.ipynb)
+4. [Reachability index](04_reachability_index.ipynb)
+5. [Topological levels](05_levels.ipynb)
+
 ## Slides
 
 This topic is covered in much more details in slides for the presentation "[_Graph operations in Git version control system_][google-drive-slides]" by Jakub Narebski (2019).

index.ipynb

@@ -82,6 +82,31 @@
     "Only the first command performs straight reachability query."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Table of contents"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "> Warning: this is not generated automatically"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "1. [Graphs in Python](01_tools.ipynb)\n",
+    "2. [Related works: various reachability labelings](02_related.ipynb)\n",
+    "3. [Example directed graphs](03_example_graphs.ipynb)\n",
+    "4. [Reachability index](04_reachability_index.ipynb)\n",
+    "5. [Topological levels](05_levels.ipynb)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},