.editorconfig

patch: add similarity config knob in experimental section

This config knob will control whether or not to show the similarity
calculation in the diff output:

  diff --git a/README.md b/foo.md
  similarity index 88%
  rename from README.md
  rename to foo.md
  --- a/README.md
  +++ b/foo.md

# See http://EditorConfig.org for the specification

root = true

[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true

[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true