Fix single-command to run demo env with docker

[josecelano]

The single command provided by the documentation to run a demo with docker did not work.

See #351

This PR only fixes that command and improves a little bit the documentation.

In the short term, we need to make some improvements described here.

In the long term, we need to make UX better. See the issue #351 for some ideas about how we can make it.

[codecov]

Codecov Report

Merging #365 (d728ddc) into develop (8f39f6e) will decrease coverage by 0.02%.
Report is 1 commits behind head on develop.
The diff coverage is 50.00%.

❗ Current head d728ddc differs from pull request most recent head 8defabd. Consider uploading reports for the commit 8defabd to get more accurate results

@@             Coverage Diff             @@
##           develop     #365      +/-   ##
===========================================
- Coverage    85.08%   85.07%   -0.02%     
===========================================
  Files           88       88              
  Lines         6564     6564              
===========================================
- Hits          5585     5584       -1     
- Misses         979      980       +1     

Files Changed	Coverage Δ
src/lib.rs	64.20% <50.00%> (-0.19%)	⬇️

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