chore(playground): update playground generator for v8 docs (#3542)

Author: mapsandapps

_templates/README.md

@@ -26,7 +26,7 @@ Once you've generated your playground, you need to add it to the main markdown f
 ```
 ## Feature
 
-import Feature from '@site/static/usage/v7/button/feature/index.md';
+import Feature from '@site/static/usage/v8/button/feature/index.md';
 
 <Feature />
 ```

_templates/playground/new/index.js

@@ -54,8 +54,8 @@ module.exports = {
               type: 'select',
               name: 'version',
               message: 'Select the Ionic Framework version for the playground',
-              initial: '7',
-              choices: ['6', '7'],
+              initial: '8',
+              choices: ['6', '7', '8'],
             },
             {
               type: 'toggle',
@@ -77,7 +77,7 @@ module.exports = {
 
             const playgroundName = changeCase.pascal(answers.path.split('/').pop());
             console.log(
-              `\nTo use this playground in a docs markdown file, include\nthe following:\n\n## ${playgroundName}\n\nimport ${playgroundName} from '@site/static/usage/v7/${answers.name}/${answers.path}/index.md';\n\n<${playgroundName} />\n`
+              `\nTo use this playground in a docs markdown file, include\nthe following:\n\n## ${playgroundName}\n\nimport ${playgroundName} from '@site/static/usage/v${answers.version}/${answers.name}/${answers.path}/index.md';\n\n<${playgroundName} />\n`
             );
 
             return answers;