Add .editorconfig file

This patch adds initial EditorConfig [1] file with sensible defaults
specific for future PHP code, HTML templates, and possible other file
types. It helps formating code and new files in editors and IDEs that
utilize EditorConfig settings. Current state of EditorConfig provides
setting identation style and level, new lines types, files encodings,
and similar basic files and code configurations.

[1] https://editorconfig.org

Author: petk

.editorconfig

@@ -0,0 +1,12 @@
+# https://editorconfig.org/
+
+root = true
+
+[*]
+charset                  = utf-8
+end_of_line              = lf
+indent_size              = 4
+indent_style             = space
+tab_width                = 4
+trim_trailing_whitespace = true
+insert_final_newline     = true