Addition of Dockerfile for version 0.11

[fgypas]

Addition of Dockerfile for version 0.11

Locally it works for me.

The commands are called without the bin prefix as shown below:

julia whippet-index.jl --help

and not

julia bin/whippet-index.jl --help

It is also available in dockerhub if someone wants to try it under the following url:
https://hub.docker.com/r/zavolab/whippet/

You can pull it locally as:
docker pull zavolab/whippet:0.11

[codecov]

Codecov Report

Merging #77 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #77   +/-   ##
=======================================
  Coverage   58.99%   58.99%           
=======================================
  Files          19       19           
  Lines        2370     2370           
=======================================
  Hits         1398     1398           
  Misses        972      972

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