add editorconfig and stylelint rules (decaporg#21)

* add editorconfig and stylelint rules

* put back markdownlint-cli

.editorconfig

@@ -0,0 +1,19 @@
+# https://editorconfig.org
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.js]
+quote_type = single
+spaces_around_operators = true
+
+[*.css]
+quote_type = single
+
+[*.md]
+trim_trailing_whitespace = false

.stylelintrc

@@ -0,0 +1,33 @@
+{
+  "processors": ["stylelint-processor-styled-components"],
+  "extends": ["stylelint-config-standard-scss", "stylelint-config-styled-components"],
+  "customSyntax": "postcss-scss",
+  "rules": {
+    "block-no-empty": null,
+    "no-duplicate-selectors": null,
+    "no-empty-source": null,
+    "no-extra-semicolons": null,
+    "declaration-empty-line-before": null,
+    "string-quotes": null,
+    "selector-class-pattern": null,
+    "selector-pseudo-element-colon-notation": null,
+    "rule-empty-line-before": null,
+    "declaration-colon-newline-after": null,
+    "at-rule-empty-line-before": null,
+    "alpha-value-notation": null,
+    "color-function-notation": null,
+    "keyframes-name-pattern": null,
+    "value-list-comma-newline-after": null,
+    "no-descending-specificity": null,
+    "selector-type-no-unknown": [
+      true,
+      {
+        "ignoreTypes": ["$dummyValue"]
+      }
+    ],
+    "value-keyword-case": [
+      "lower",
+      { "ignoreKeywords": ["dummyValue"], "camelCaseSvgKeywords": true }
+    ]
+  }
+}