Fixed titles for the kjillionth time

docs/build.md

@@ -1,3 +1,7 @@
+# TeraHz build guide
+This document describes the process of building/installing TeraHz from the Git
+repository.
+
 ## Warning
 The recommended way of getting TeraHz is the official Raspberry Pi SD card image
 provided under the releases tab in the GitHub repository. Installing TeraHz from

docs/dependencies.md

@@ -1,3 +1,4 @@
+# Development-stable dependencies
 The current development version of TeraHz has been verified to work with:
 
   - Raspbian Stretch (9)

docs/index.md

@@ -1 +1,3 @@
-This is the start page for the TeraHz documentation.
+<img alt="TeraHz logo" src="imgs/logo-sq.png" width="200px">
+# TeraHz documentation - index
+This is the starting point of TeraHz documentation.