add titles to clef docs (#19384)

docs/_clef/Overview.md

@@ -1,3 +1,8 @@
+---
+title: Clef overview
+---
+
+
 Clef
 ===
 _A reasonably secure wallet_

docs/_clef/Rules.md

@@ -1,3 +1,7 @@
+---
+title: Rules
+---
+
 # Rules
 
 The `signer` binary contains a ruleset engine, implemented with [OttoVM](https://github.com/robertkrimen/otto)

docs/_clef/Setup.md

@@ -1,3 +1,8 @@
+---
+title: Advanced setup
+---
+
+
 # Setting up Clef
 
 This document describes how Clef can be used in a more secure manner than executing it from your everyday laptop, 

docs/_clef/Tutorial.md

@@ -1,3 +1,7 @@
+---
+title: Tutorial
+---
+
 ## Initializing the signer
 
 First, initialize the master seed.

docs/_clef/apis.md

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+---
+title: Communication APIs
+---
+
 ## Communication
 
 ### External API

docs/_clef/datatypes.md

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+---
+title: Communication data types
+---
+
+
 ## UI Client interface
 
 These data types are defined in the channel between clef and the UI