New Maintainer candidate: Edward Mack (#219)

I propose adding Edward Mack from Chainsafe Systems as a maintainer for Besu.

Edward has been instrumental to adding the support for Ethereum Classic
and their two testnets Kotti and Mordor. Since Classic support is not
strategic to ConsenSys or Web3Labs it is safe to say that without his
contribution and continued involvement Ethereum Classic support would
not have happened. Because Ethereum Classic has some ambitious changes
slated for the next year promoting Edward to Maintainer will further
secure future support for it in Hyperledger Besu.

Voting ends two weeks from today, 2am UTC on 2019-12-10
https://www.timeanddate.com/countdown/to?iso=20191210T02&p0=1440

For more information on this process see the Becoming a Maintainer
section in the MAINTAINERS.md file.

Signed-off-by: Danno Ferrin <danno.ferrin@gmail.com>
Signed-off-by: Edward Evans <edjojob@gmail.com>

MAINTAINERS.md

@@ -11,6 +11,7 @@
 | Byron Gravenorst | bgravenorst      | bgravenorst      |
 | Chris Hare       | CjHare           | cjhare           |
 | Edward Evans     | EdJoJob          | EdJoJob          |
+| Edward Mack      | edwardmack       | mackcom          | 
 | Ivaylo Kirilov   | iikirilov        | iikirilov        |
 | Jason Frame      | jframe           | jframe           |
 | Joshua Fernandes | joshuafernandes  | joshuafernandes  |