Add markets to home/ welcome page

Feature request:

Add arbitrage enabling markets such as the following to the home page:

open.btc-bridge.btc
Gdex.eth-sparkdex.eth
Rudex.btc-bridge.btc

These markets are extremely important to bitshares as when they are liquid they allow and increase trade activity of arb bots. They affectively extend and combine liquidity accross our markets. More activity is more fees for exchanges and the blockchain.

These markets are a unique feature of bitshares and should be promoted.

Start by locating the home or welcome page implementation and the existing list of promoted markets. Add the three requested markets to that list, then verify that they appear correctly on the home page.

Written by the indexing model from the issue text.