[README] Add 'Getting Started' step to load sem doms

[imnasnainaec]

Resolves #3159

To review this pr, check out the README in this branch:

• Does the placement of the new step make sense in the README?
• Is the instruction clear, concise, correct, and without spelling/grammar errors?
• Do the links work?

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.82%. Comparing base (457eafe) to head (2c2aa71).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3230      +/-   ##
==========================================
- Coverage   74.87%   74.82%   -0.05%     
==========================================
  Files         277      277              
  Lines       10622    10622              
  Branches     1270     1270              
==========================================
- Hits         7953     7948       -5     
- Misses       2306     2310       +4     
- Partials      363      364       +1     

Flag	Coverage Δ
backend	83.84% <ø> (-0.11%)	⬇️
frontend	66.83% <ø> (ø)

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[andracc]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @imnasnainaec)