README: Fix link to Docker docs

[olleolleolle]

This changes the readme so that the internal link to the documentation on Docker usage works.

[zubot]

This change is 

[codecov]

Codecov Report

Merging #1024 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1024      +/-   ##
============================================
- Coverage     36.85%   36.84%   -0.01%     
  Complexity     6139     6139              
============================================
  Files          1649     1649              
  Lines         65407    65392      -15     
  Branches       7622     7617       -5     
============================================
- Hits          24105    24096       -9     
+ Misses        39205    39199       -6     
  Partials       2097     2097

Impacted Files	Coverage Δ	Complexity Δ
...ontend/src/app/editor/reducers/settings-reducer.js	80.45% <0%> (-0.23%)	0% <0%> (ø)
...r/reducers/phrase-reducer/filter-status-reducer.js	100% <0%> (ø)	0% <0%> (ø)	⬇️
...end/src/app/editor/reducers/suggestions-reducer.js	100% <0%> (ø)	0% <0%> (ø)	⬇️
...nd/src/app/editor/reducers/phrase-reducer/index.js	85.62% <0%> (+2.88%)	0% <0%> (ø)	⬇️

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[djansen-redhat]

@olleolleolle thanks for the fix!