Add information for gsoc-2021

[kunaltyagi]

Hey @divmadan, @tin1254, @ueqri

Could you take a look at the gsoc-2020 folder, and create PRs for adding your content on the PCL website?

TODO for me: Create a PR to add a separate GSoC page as well as change the quick link to GSoC 2021

[tin1254]

PR