Create .editorconfig

I think it'd be a good idea to add an `.editorconfig` to the projects root for contributors to easily see the code-formatting style as is common with most Open Source projects.

.editorconfig

@@ -0,0 +1,20 @@
+# https://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+trim_trailing_whitespace = true
+
+[*.go]
+indent_size = 8
+indent_style = tab
+
+[*.js]
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false