Introduce main page: index and empty usage (#433)

docs/index.md

+---
+hide:
+  - toc
+  - navigation
+---
+
+<center>
+# Welcome
+
+![silkaj logo](images/silkaj_logo.png){ width="200" }
+
+Welcome to Silkaj documentation
+
+[Install :material-package-down:](/install){ .md-button .md-button--primary } [Usage :material-keyboard-outline:](/usage){ .md-button .md-button--primary }
+
+## What is Silkaj?
+
+Silkaj is a command line client for [Ğ1](https://duniter.org/g1/) libre currency powered by [Duniter software](https://duniter.org/).
+
+<div class="grid cards" markdown>
+
+- :fontawesome-solid-money-bill-1-wave:{ .lg .middle} __Money management__
+
+    ______________________________________________________________________
+
+    Transfer money, check your balance, and history stand.
+
+- :material-vector-polyline:{ .lg .middle } __Web-of-Trust__
+
+    ______________________________________________________________________
+
+    Manage your certifications, membership, and the revocation document
+
+- :octicons-terminal-16:{ .lg .middle } __CLI interface__
+
+    ______________________________________________________________________
+
+    Silkaj is built around a command line interface design.
+
+- :material-book-open-variant:{ .lg .middle} __RTM compatible__
+
+    ______________________________________________________________________
+
+    Silkaj is compatible with the [Relative Theory of Money](https://en.trm.creationmonetaire.info/)
+    and includes Ğ1 Monetary License.
+
+- :material-scale-balance:{ .lg .middle } __Free software__
+
+    ______________________________________________________________________
+
+    Silkaj is licensed under :material-copyleft: :simple-gnu: [GNU AGPL v3](https://www.gnu.org/licenses/agpl-3.0.html).
+
+- :material-raspberry-pi:{ .lg .middle } __Low requirements__
+
+    ______________________________________________________________________
+
+    Written with Python, Silkaj is built with low requirements in mind.
+
+<!--
+- Authentication method
+
+    ______________________________________________________________________
+
+    Wallet Import Format (WIF) is implemented.
+-->
+
+</div>
+</center>

docs/usage.md

+# Usage
+
+Documentation to be written.

mkdocs.yml

@@ -46,9 +46,10 @@ markdown_extensions:
   - toc:
       permalink: true
 nav:
-  - index.md
+  - Home: index.md
   - Installation: install.md
   - Usage:
+    - usage.md
     - multi-recipients_transfers_and_automation.md
     - DeathReaper: deathreaper.md
   - Blog: