index: use templates for the index route

Signed-off-by: Gunwant Jain <mail@wantguns.dev>

templates/index.html.tera

@@ -0,0 +1,33 @@
+{% extends "base" %}
+
+{% block body %}
+<pre> <code>
+USAGE
+-----
+
+    POST    / 
+
+        accepts raw data in the body of the request and responds with a URL
+        of a page containing the body's content
+
+    GET     /<id>
+
+        retrieves the content for the paste with id `<id>`
+
+    GET     /p/<id>
+
+        retrieves the HTML page with syntax-highlighted content for the paste with id `<id>`
+
+EXAMPLES
+--------
+
+    Paste a file named 'file.txt' using cURL:
+
+        curl --data-binary @file.txt https://bin.wantguns.dev
+
+    Paste from stdin using cURL:
+
+        echo \"Hello, world.\" | curl --data-binary @- https://bin.wantguns.dev
+
+    </code> </pre>
+{% endblock body %}