add MegaLinter, .editorconfig and style fixes

.editorconfig

@@ -0,0 +1,31 @@
+root = true
+
+# Global
+[*]
+indent_style = unset
+indent_size = 4
+tab_width = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = unset
+
+# Source
+[*.{sh,bash,dash,ksh}]
+indent_style = tab
+insert_final_newline = true
+
+[builder]
+insert_final_newline = true
+
+# Other
+[*.md]
+trim_trailing_whitespace = false
+
+[*.yml]
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+
+[*.{txt,cfg,conf}]
+indent_style = tab