Add editorconfig to maintain consistent style (#1486)

EditorConfig should help us maintain consistent style across different
editors. Many editors have native support; others have plugins.

Website: https://editorconfig.org/

.editorconfig

@@ -0,0 +1,17 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+[*.{py,pyx,pxd}]
+indent_style = space
+indent_size = 4
+
+# Follow Linux kernel coding style
+[*.{c,h,cpp,hpp,inc}]
+indent_style = tab
+indent_size = 8
+
+[Makefile]
+indent_style = tab