message: add headers for source code
diff: # Exchange
  **Reference Implementation:** https://origin-ui-canary.herokuapp.com/exchange/view-market
  -Source code on github: https://github.com/energywebfoundation/origin/tree/master/packages/trade
  +**Source code on github:** https://github.com/energywebfoundation/origin/tree/master/packages/trade
  The Exchange interface enables efficient and transparent order book trading between sellers and buyers. It integrates with certificate issuance to allow for trading of [Energy Attribute Certificates (EACs)](./user-guide-glossary.md#energy-attribute-certificate) on the blockchain.
  