Implement Test Button in Nav Bar

[superxgen]

Site update is nearly ready, and we'd like to begin testing.

To support this, and future tests, we'd be benefitted by a button in our navigation that leads to our development branch.

Suggesting we add that now, as implied in this figma draft, and deploy our updates to this branch for testing.
https://www.figma.com/file/O9VBPoKQH80YLndvcbj3Zf/%5BMVP%5D-HomePage-2.0?type=design&node-id=122%3A30146&mode=design&t=6qiYQt6hvMCH86Rj-1

implementing the test button in the nav bar to lead to our development branch (https://test.nearbuilders.org) will accelerate our testing and update cycle, and open up the process to a broader team/community.

[Megha-Dev-19]

Just a thought:
May be we should also have an option on develop to shift between testnet and mainnet
like potlock wouldn't work on testnet, afaik it only have mainnet staging and production account.