chore: .editorconfig, .gitattributes

[dkarlovi]

This adds two QoL files.

.editorconfig

Ensures a baseline of file formatting across all files added to the repo, see https://editorconfig.org/

.gitattributes

Removes everything not required for production from the Git export of the repo, which is used by Github to create releases used by Composer. This is considered best practice and done by a lot of packages already, see https://twitter.com/dkarlovi/status/1098495571214692352

[codecov]

Codecov Report

Merging #207 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #207   +/-   ##
=========================================
  Coverage     91.56%   91.56%           
  Complexity      312      312           
=========================================
  Files            36       36           
  Lines           735      735           
=========================================
  Hits            673      673           
  Misses           62       62           

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[dkarlovi]

Suggest merging this one after #205 so there's no conflicts.