ADD .editorconfig to display source files in Gitea with tab size of 4

.editorconfig

@@ -0,0 +1,22 @@
+# EditorConfig: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# General settings
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+
+# Source code files
+[*.{c,h,s}]
+indent_style = tab
+charset = utf-8
+indent_size = 4
+trim_trailing_whitespace = true
+
+# Tab indentation (no size specified)
+[{Makefile,*.mk}]
+indent_style = tab
+trim_trailing_whitespace = false