Add prettier and stylelint config files

.prettierignore

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+vendor

.prettierrc.js

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+// Import the default config file and expose it in the project root.
+// Useful for editor integrations.
+module.exports = require( '@wordpress/prettier-config' );

.stylelintignore

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+node_modules
+vendor

.stylelintrc.json

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+{
+	"extends": "@wordpress/stylelint-config/scss",
+	"rules": {
+		"at-rule-empty-line-before": null,
+		"at-rule-no-unknown": null,
+		"comment-empty-line-before": null,
+		"font-weight-notation": null,
+		"max-line-length": null,
+		"no-descending-specificity": null,
+		"rule-empty-line-before": null,
+		"selector-class-pattern": null,
+		"value-keyword-case": null,
+		"scss/operator-no-unspaced": null,
+		"scss/selector-no-redundant-nesting-selector": null,
+		"scss/at-import-partial-extension": null,
+		"scss/no-global-function-names": null,
+		"scss/comment-no-empty": null,
+		"scss/at-extend-no-missing-placeholder": null,
+		"scss/operator-no-newline-after": null,
+		"scss/at-if-closing-brace-newline-after": null,
+		"scss/at-else-empty-line-before": null,
+		"scss/at-if-closing-brace-space-after": null,
+		"no-invalid-position-at-import-rule": null
+	}
+}