Lesson 1 cleanup

[jaygiang]

• Remove PWA lesson(move to a later lesson)
• Install Docusaurus Canary release to allow count start for showLineNumbers in code snipped
  • This feature will eventually be release in stable version v.38
• Add showLineNumber=start-number to lesson-1.mdx

[theangchen]

As a newbie coming to the docs, I think we need to keep the portion of "Getting Started" that shows them how to get the app up and running on localhost before we dive into adding button functionality in code. So they know where to look to see their changes.

[theangchen]

Worked through Lesson 1 ✅ LGTM

[jaygiang]

@theangchen removed the diffs from GridContainer snippet and added showLineNumber to the import snippet. Please review.

[theangchen]

✅ LGTM