Moved parts of the html separate files

templates/auth.html

@@ -1,12 +1,4 @@
-<!doctype html>
-<html lang="en">
-    <head>
-        <title>Shopping List</title>
-         <!-- Latest compiled and minified CSS -->
-        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css">
-        <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
-        <link rel="stylesheet" content="text/css" href="/static/css/main.css"/>
-    </head>
+ {% include "header.html" %}
     <body>
         <h1 class="container" style="text-align: center">{{ data["title"] }}</h1>