add .editorconfig file #29

Job	Run time
Unit tests / Linux (5.9)	2m 50s
Unit tests / Linux (5.10)	2m 45s
Unit tests / Linux (6.0)	2m 53s
Unit tests / Linux (nightly-6.0)	3m 19s
Unit tests / Linux (nightly-main)	3m 22s
Soundness / API breakage check	2m 37s
Soundness / License headers check	4s
Soundness / Documentation check	2m 12s
Soundness / Unacceptable language check	5s
Soundness / Broken symlinks check	2s
Soundness / Format check	38s
Soundness / Python lint check	4s
Soundness / Shell check	31s
Soundness / YAML lint check	4s
Cxx interop / Cxx interop / Linux (5.9)	1m 43s
Cxx interop / Cxx interop / Linux (5.10)	1m 49s
Cxx interop / Cxx interop / Linux (6.0)	1m 54s
Cxx interop / Cxx interop / Windows (6.0)	7s
Cxx interop / Cxx interop / Windows (nightly-6.0)	1s
Cxx interop / Cxx interop / Linux (nightly-6.0)	2m 18s
Cxx interop / Cxx interop / Windows (nightly-main)	1s
Cxx interop / Cxx interop / Linux (nightly-main)	2m 15s
	31m 34s

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