Add protected option to text selection plugin

[cdrini]

Closes #1140

Issues:

• Not allowing selection at all on FF Android
• Difficult to test on safari because of #1129

[codecov[bot]]

Codecov Report

Merging #1142 (d03fe4a) into master (7914dfa) will decrease coverage by 0.14%. The diff coverage is 21.42%.

:exclamation: Current head d03fe4a differs from pull request most recent head 744192d. Consider uploading reports for the commit 744192d to get more accurate results

@@            Coverage Diff             @@
##           master    #1142      +/-   ##
==========================================
- Coverage   70.24%   70.10%   -0.14%     
==========================================
  Files          61       61              
  Lines        5162     5175      +13     
  Branches     1066     1071       +5     
==========================================
+ Hits         3626     3628       +2     
- Misses       1509     1520      +11     
  Partials       27       27              

Impacted Files	Coverage Δ
src/plugins/plugin.text_selection.js	79.43% <21.42%> (-2.75%)	:arrow_down: