Migrate to Mozilla's webextension-polyfill package

[eejdoowad]

Type of Change

Put an [x] for the relevant option

• [x] Bugfix/Cleanup (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Summary Of Changes

Why is this change needed?

Mozilla authors and supports the webextension-polyfill package so we don't have to.

Does this close any open issues?

No

Checklist

• [x] Tests are passing locally
• [x] Updated the README/Wiki documentation (if relevant)

Additional Comments

Add any additional comments you may have here.

[codecov-io]

Codecov Report

Merging #97 into master will increase coverage by 0.24%. The diff coverage is 0%.

@@            Coverage Diff            @@
##           master     #97      +/-   ##
=========================================
+ Coverage   58.26%   58.5%   +0.24%     
=========================================
  Files          58      57       -1     
  Lines         714     711       -3     
  Branches       65      65              
=========================================
  Hits          416     416              
+ Misses        267     264       -3     
  Partials       31      31

Impacted Files	Coverage Δ
src/options/Main/OptionsList/index.jsx	100% <ø> (ø)	:arrow_up:
src/saka/index.jsx	0% <ø> (ø)	:arrow_up:
src/suggestion_engine/server/providers/history.js	100% <ø> (ø)	:arrow_up:
src/suggestion_engine/server/providers/bookmark.js	100% <ø> (ø)	:arrow_up:
src/lib/url.js	88.88% <ø> (ø)	:arrow_up:
...rc/suggestion_engine/server/providers/closedTab.js	96.55% <ø> (ø)	:arrow_up:
src/options/saka-options.jsx	0% <ø> (ø)	:arrow_up:
src/suggestion_engine/server/index.js	95.23% <ø> (ø)	:arrow_up:
src/suggestion_engine/server/providers/tab.js	100% <ø> (ø)	:arrow_up:
src/saka/Main/index.jsx	21.87% <ø> (ø)	:arrow_up:
... and 5 more

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