Added new interface image

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Added lesson plan and solution

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Changed custom CSS to bootstrap class

Signed-off-by: Shivam Dixit <shivamd001@gmail.com>
Added lesson Useful Tools

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