[MINOR UPDATE]: Add an .editorconfig file providing style hints to editors and IDEs (#2281)
* Add an EditorConfig file providing style hints to editors and IDEs.
EditorConfig (https://editorconfig.org/) is an editor-neutral file format
that holds code style settings. This particular config has been defined
to reflect the style convetions in the Drill codebase (most significantly,
indentation is with 2 spaces). Most mainstream editors and IDEs will
recognise this file and set themselves up accordingly, making it easier to
contribute code following the project's conventions.
Note that .editorconfig only contains global conventions for codebase, not
individual users' editor preferences, which must be masked by .gitignore.
Other Apache projects with a .editorconfig file in their code repo are
Superset, Subversion, Thrift, Submarine and presumably some more.
* Add Apache licence header to .editorconfig.
