Add e2e test config

[dominik-zeglen]

I want to merge this change because it adds e2e test environment config.
Execute npm run test-e2e to run tests.

Pull Request Checklist

1. Privileged views and APIs are guarded by proper permission checks.
2. All visible strings are translated with proper context.
3. All data-formatting is locale-aware (dates, numbers, and so on).
4. Database queries are optimized and the number of queries is constant.
5. Database migration files are up to date.
6. The changes are tested.
7. The code is documented (docstrings, project documentation).
8. GraphQL schema and type definitions are up to date.
9. Changes are mentioned in the changelog.

[codecov]

Codecov Report

Merging #4553 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4553   +/-   ##
=======================================
  Coverage   90.89%   90.89%           
=======================================
  Files         296      296           
  Lines       17435    17435           
  Branches     1734     1734           
=======================================
  Hits        15847    15847           
  Misses       1082     1082           
  Partials      506      506

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[django-queries]

Here is the report for c4ae72a (mirumee/saleor @ add/testcafe)
Base comparison is 328ddb0.

No differences were found. (click me)

# api.benchmark checkout
  test name                           	left count 	right count	duplicate count
  ------------------------------------	-----------	-----------	---------------
  add billing address to checkout     	         34	         34	             20
  add shipping to checkout            	          7	          7	              0
  checkout payment charge             	         14	         14	              0
  complete checkout                   	          6	          6	              0
  create checkout                     	         41	         41	             20

# api.benchmark homepage
  test name                           	left count 	right count	duplicate count
  ------------------------------------	-----------	-----------	---------------
  retrieve main menu                  	          5	          5	              0
  retrieve product list               	          4	          4	              0
  retrieve secondary menu             	          5	          5	              0
  retrieve shop                       	          2	          2	              0

# api.benchmark product
  test name                           	left count 	right count	duplicate count
  ------------------------------------	-----------	-----------	---------------
  product details                     	         13	         13	              3

# api.benchmark variant
  test name                           	left count 	right count	duplicate count
  ------------------------------------	-----------	-----------	---------------
  retrieve variant list               	          9	          9	              2