Add more web frontend functionalities

[sayanarijit]

Is your feature request related to a problem? Please describe.

We can pass many parametets from the command-line using http headers. But the web frontend is still lacking in functionalities. It can only generate SVG images and print the PDF, which is rather limited.

Describe the solution you'd like

Add a minimized "Advanced" button, clicking which we get more options. Options like download png/jpeg, set dimensions etc.

Describe alternatives you've considered

None

Additional context

The UI needs to be simple and easy to use. By default, users shouldn't be able to see all the buttons. Only by clicking the "Advanced" button, all the customisation options should appear.
Also, we need to keep the website lightweight. Let's avoid using external libraries as much as possible.