closes #509 Document JavaScript coding guidelines

.browserslistrc

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+defaults
+not ie 11

.editorconfig

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+# http://editorconfig.org
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+# Use 4 spaces for the Python files
+[*.py]
+indent_size = 4
+max_line_length = 80
+
+# The JSON files contain newlines inconsistently
+[*.json]
+indent_size = 4
+insert_final_newline = ignore
+
+# No need to use the spaces for contents.lr file
+[*.lr]
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = ignore
+insert_final_newline = ignore
+
+# No need to use the spaces for .ini files
+[*.ini]
+indent_style = ignore
+insert_final_newline = ignore
+
+# Minified JavaScript files shouldn't be changed
+[**.min.js]
+indent_style = ignore
+insert_final_newline = ignore
+
+# Makefiles always use tabs for indentation
+[Makefile]
+indent_style = tab
+
+# Batch files use tabs for indentation
+[*.bat]
+indent_style = tab
+
+[*.md]
+trim_trailing_whitespace = false
+