Link back to tBTC website from the footer and the header

[liz-shinn]

Add a link back to the tBTC website from the dApp. Can implement this by clicking on the tbtc logo that's in the header, as well as the tbtc logo that's in the footer and have those images be links.

Also, the about link is linking incorrectly to cross-chain group. It should link to this about page from tbtc: https://tbtc.network/about

[liz-shinn]

^ footer

The tbtc logo image here would link back to https://tbtc.network/
and the About link should link to https://tbtc.network/about

[Shadowfiend]

Making the logo link to the main page is going to be a bigger thing, but I fixed the about link 5161665.

[benlongstaff]

At the moment it doesn't look like the config has tbtc info site so i just added a link back to the dapps homepage.
#376

After I finish minting thats the page I want to go back to ;)