Add missing spellcheck param to character count

We added a new spellcheck param to the textarea component in #1859

However, we forgot to add the param to the character count component, which meant it couldn't be passed through to the textarea. This adds the missing param.

src/govuk/components/character-count/character-count.test.js

@@ -4,6 +4,8 @@ const configPaths = require('../../../../config/paths.json')
 const PORT = configPaths.ports.test
 const baseUrl = `http://localhost:${PORT}`
 
+const { render } = require('../../../../lib/jest-helpers')
+
 const goToExample = (exampleName = false) => {
   const url = exampleName
     ? `${baseUrl}/components/character-count/${exampleName}/preview`
@@ -143,6 +145,36 @@ describe('Character count', () => {
       })
     })
 
+    describe('when it has the spellcheck attribute', () => {
+      it('renders the textarea with spellcheck attribute set to true', () => {
+        const $ = render('character-count', {
+          spellcheck: true
+        })
+
+        const $component = $('.govuk-character-count .govuk-textarea')
+        expect($component.attr('spellcheck')).toEqual('true')
+      })
+
+      it('renders the textarea with spellcheck attribute set to false', () => {
+        const $ = render('character-count', {
+          name: 'my-char-count-name',
+          spellcheck: false
+        })
+
+        const $component = $('.govuk-character-count .govuk-textarea')
+        expect($component.attr('spellcheck')).toEqual('false')
+      })
+
+      it('renders the textarea without spellcheck attribute by default', () => {
+        const $ = render('character-count', {
+          name: 'my-char-count-name'
+        })
+
+        const $component = $('.govuk-character-count .govuk-textarea')
+        expect($component.attr('spellcheck')).toBeUndefined()
+      })
+    })
+
     describe('when counting words', () => {
       it('shows the dynamic message', async () => {
         await goToExample('with-word-count')

src/govuk/components/character-count/character-count.yaml

@@ -59,6 +59,10 @@ params:
   type: object
   required: false
   description: HTML attributes (for example data attributes) to add to the textarea.
+- name: spellcheck
+  type: boolean
+  required: false
+  description: Optional field to enable or disable the spellcheck attribute on the character count.
 - name: countMessage
   type: object
   required: false

src/govuk/components/character-count/template.njk

@@ -10,6 +10,7 @@
     name: params.name,
     describedBy: params.id + '-info',
     rows: params.rows,
+    spellcheck: params.spellcheck,
     value: params.value,
     formGroup: params.formGroup,
     classes: 'govuk-js-character-count' + (' govuk-textarea--error' if params.errorMessage) + (' ' + params.classes if params.classes),