Drafttopic: Add fetch text utility for fetching page text for labelings

[codez266]

https://phabricator.wikimedia.org/T183355

[codecov]

Codecov Report

Merging #14 into master will increase coverage by 2.37%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #14      +/-   ##
==========================================
+ Coverage   50.65%   53.02%   +2.37%     
==========================================
  Files          10       12       +2     
  Lines         535      628      +93     
==========================================
+ Hits          271      333      +62     
- Misses        264      295      +31

Impacted Files	Coverage Δ
drafttopic/utilities/tests/test_fetch_text.py	100% <100%> (ø)
drafttopic/utilities/fetch_text.py	59.74% <59.74%> (ø)

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[adamwight]

The associated task was declined, so I'm assuming this wasn't needed. We can reopen if that's wrong.