build: let webpack proxy server handle more content encoding

[ktmud]

SUMMARY

A small tweak for local dev-server (npm run dev-server) proxying to a production Superset service. Sometimes production Superset backend runs behind nginx servers with different compression configuration. This PR allows the dev the dev server to be able to handle both Brotli and Deflate compression, in addition to gzip.

cc @kristw

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TEST PLAN

1. Start Superset Flask server, put it behind nginx with Brotli enabled
2. Start Superset frontend dev server and proxy it the backend by npm run dev-server --superset http://{your_server_url}
3. You should see the page correctly rendered instead of garbled text.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-io]

Codecov Report

Merging #11376 into master will decrease coverage by 4.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #11376      +/-   ##
==========================================
- Coverage   65.78%   61.57%   -4.22%     
==========================================
  Files         838      838              
  Lines       39845    39842       -3     
  Branches     3655     3655              
==========================================
- Hits        26214    24534    -1680     
- Misses      13531    15127    +1596     
- Partials      100      181      +81     

Flag	Coverage Δ
#cypress	?
#javascript	62.63% <ø> (ø)
#python	60.94% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset-frontend/src/SqlLab/App.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/App.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/dashboard/App.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/index.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/dashboard/index.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/setup/setupColors.js	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/chart/ChartContainer.jsx	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/setup/setupFormatters.js	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/explore/reducers/index.js	0.00% <0.00%> (-100.00%)	⬇️
superset-frontend/src/setup/setupPluginsExtra.js	0.00% <0.00%> (-100.00%)	⬇️
... and 167 more

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[graceguo-supercat]

LGTM