Fix broken links.

[Yshuo-Li]

Fix broken links in getting_started.md.

[codecov]

Codecov Report

Merging #236 (2779707) into master (2827d93) will not change coverage.
The diff coverage is n/a.

❗ Current head 2779707 differs from pull request most recent head 8e96714. Consider uploading reports for the commit 8e96714 to get more accurate results

@@           Coverage Diff           @@
##           master     #236   +/-   ##
=======================================
  Coverage   81.79%   81.79%           
=======================================
  Files         152      152           
  Lines        7223     7223           
  Branches     1066     1066           
=======================================
  Hits         5908     5908           
  Misses       1191     1191           
  Partials      124      124           

Flag	Coverage Δ
unittests	81.79% <ø> (ø)

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