Fix title display for all pages (#776)

- Fix Index page to show just `Black Python Devs` instead of `Index | Black Python Devs`
- Fix other pages to show proper `<page-title> | Black Python Devs` format

Author: dragid10

_layouts/default.html

@@ -4,7 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1" />
     <meta name="description" content="{% if description%}{{ description | escape }}{% else %}{{ site.description }}{% endif %}" />
-    <title>{% if title %}{{ site.title }} | {{ title }}{% else %}{{ site.title }}{% endif %}</title>
+    <title>{% if title == 'Index' %}Black Python Devs{% elif title %}{{ title }} | Black Python Devs{% else %}Black Python Devs{% endif %}</title>
     <link rel="stylesheet" href="{{ '/assets/css/pico.min.css' }}" />
     <link rel="stylesheet" href="{{ '/assets/css/pico.colors.min.css' }}" />
     <link rel="stylesheet" href="{{ '/assets/css/bpd.css' }}" />