build:增加格式化说明。

.editorconfig

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+# http://editorconfig.org
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+trim_trailing_whitespace = true
+insert_final_newline = true
+charset = utf-8

.prettierrc

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+{
+  "bracketSpacing": true,
+  "jsxBracketSameLine": true,
+  "tabWidth": 2,
+  "useTabs": false,
+  "semi": true,
+  "singleQuote": false,
+  "jsxSingleQuote": false,
+  "trailingComma": "all",
+  "arrowParens": "always"
+}