DOCS-#447: Add note about installation and setup in README

[cgarciae]

Overview

Its not a full solution for wrong installations but having a small note at the beginning of the Getting Started that guides users to correctly installing lux-api instead of lux and informing/reminding them they need to install the jupyter extension might help on this regard.

[codecov]

Codecov Report

Merging #449 (fe62e5d) into master (a7e2cf7) will decrease coverage by 0.04%.
The diff coverage is n/a.

❗ Current head fe62e5d differs from pull request most recent head 27b76fc. Consider uploading reports for the commit 27b76fc to get more accurate results

@@            Coverage Diff             @@
##           master     #449      +/-   ##
==========================================
- Coverage   65.65%   65.60%   -0.05%     
==========================================
  Files          55       55              
  Lines        4440     4440              
==========================================
- Hits         2915     2913       -2     
- Misses       1525     1527       +2     

Impacted Files	Coverage Δ
lux/vislib/altair/Heatmap.py	93.10% <0.00%> (-3.45%)	⬇️
lux/vislib/altair/ScatterChart.py	93.93% <0.00%> (-3.04%)	⬇️

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