Add websites

[ishita-gambhir]

Websites such codingblocks and codingninjas can also be added since they regularly host contests and there's a good prize money involved(usually) too.

[nishanthvijayan]

Do they have an API or a page that can scraped easily that contain information like contest name, url, start time and end time? If yes, then they can be added

[GauravMohla]

I can raise a PR for codingninjas. They internally hit an API that can be leveraged.

[GauravMohla]

raised nishanthvijayan/CoderCalendar-API#3 for API change. will do the needful here soon. UI PR: #10

[emWolf09]

Can we have functionality to filter list based on hackathon, competitive challenges etc.