Minor UI changes
Added lesson HTML Field Restrictions
Added template for lesson

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Minor changes in comments

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Added lesson Exploiting Hidden Fields

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>