templates/form.html: Add Github fork me ribbon

[Chirag0111]

This PR adds a Github fork me ribbon in form.html.

Closes https://github.com/manu-chroma/username-availability-checker/issues/126

[manu-chroma]

this is duplicated code from status.html

We can avoid duplicating by refactoring github icon css into main css file.

[Chirag0111]

@utkarsh2102, I have done the work.

• Added proper indentation, as asked by @utkarsh2102 and @jayvdb.
• Extracted css to main.css, as asked by @manu-chroma.

Please check the same.

[manu-chroma]

Hi, The changes look good to me. @utkarsh2102 the hover effect is working for me perfectly fine locally.

@Chirag0111 I've merged master into your branch and made some linting changes Can you allow me to push to your remote branch? Refer: https://help.github.com/articles/allowing-changes-to-a-pull-request-branch-created-from-a-fork/

[utkarsh2102]

Oh, that's awesome. I will ask him to do so and would approve the task once he submits the same.

[Chirag0111]

Done.

[utkarsh2102]

Okay, nice. Approving your work.

[manu-chroma]

:tada: