Add "error" severity level to rules in preset, fixes RichardLitt#36

index.js

@@ -1,9 +1,9 @@
 exports.plugins = [
-  require('remark-lint-appropriate-heading'),
-  require('./rules/file-stem'),
-  require('./rules/file-extension'),
-  require('./rules/require-file-extension'),
-  require('./rules/no-unknown-sections'),
-  require('./rules/require-sections'),
-  require('./rules/section-order')
+  [require('remark-lint-appropriate-heading'), ['error']],
+  [require('./rules/file-stem'), ['error']],
+  [require('./rules/file-extension'), ['error']],
+  [require('./rules/require-file-extension'), ['error']],
+  [require('./rules/no-unknown-sections'), ['error']],
+  [require('./rules/require-sections'), ['error']],
+  [require('./rules/section-order'), ['error']]
 ]

lint-readme/require-rules-listing.js

@@ -10,7 +10,7 @@ module.exports = rule(
     const rules = select.selectAll('listItem link inlineCode', rulesList)
     const foundRules = rules.map((rule) => rule.value)
 
-    const expectedRules = preset.plugins.map((rule) => rule.displayName)
+    const expectedRules = preset.plugins.map(([rule]) => rule.displayName)
 
     foundRules.forEach((rule) => {
       if (!expectedRules.includes(rule)) {