Update docstring for detect.py

[philip-khor]

from rootpath import rootpath does not work - updated docs to reflect this.

[codecov]

Codecov Report

Merging #2 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #2   +/-   ##
=======================================
  Coverage   90.78%   90.78%           
=======================================
  Files           3        3           
  Lines          76       76           
=======================================
  Hits           69       69           
  Misses          7        7

Impacted Files	Coverage Δ
rootpath/detect.py	91.42% <ø> (ø)	⬆️

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[grimen]

Thank you!