Add release notes for version 2.1.0

[codecov[bot]]

Codecov Report

Merging #205 (1f0ac03) into master (be369f1) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #205   +/-   ##
=======================================
  Coverage   96.14%   96.14%           
=======================================
  Files           8        8           
  Lines         493      493           
  Branches       92       92           
=======================================
  Hits          474      474           
  Misses          9        9           
  Partials       10       10           

Impacted Files	Coverage Δ
w3lib/html.py	95.49% <0.00%> (ø)

[Gallaecio]

Let’s get https://github.com/scrapy/w3lib/pull/206 into the release.

[wRAR]

Done!