Chore updates for storybook 6 2

[jonniebigodes]

With this pull request, the Intro to Storybook tutorial is updated to Storybook 6.2
What was done:

• The React, Angular, Svelte, Vue, Ember versions of the tutorial were updated to Storybook 6.2
• Some of the videos and images related to the tutorial were updated for 6.2
• The Simple component chapter, more specifically the Unit testing section, was updated to include a reference to the Testing library as opposed to Jest, just to clarify the context.
• The Vue version was updated to Vue 3
• The gatsby-config.js configuration object was updated to 6.2

Closes:

• Removed unnecessary curly bracket #479
• Fix typo in intro-to-storybook testing docs #464
• Syntax error in the documentation #480
• Error with CLI token #477
• Snapshot Testing fails in Intro to Storybook for Angular in 'Simple Component' Step. #476

Addresses:

• Vue with TypeScript Example Configs Missing #92

With this I would like to ask:

• @josegarciamanez as you're working on the Spanish translation in Update Angular Spanish tutorial to the English version #478 if you could adjust accordingly when the pull request is merged.
• @nagashimam and @chameleonhead as you've been working on the Japanese translation in Translation of Intro to Storybook for Angular into Japanese #466 if you could adjust accordingly. Specially @chameleonhead as you spearheaded the React translation.
• @ymcheung as you're working on the Taiwanese translation in Update Intro to Storybook for React in zh-TW #441
• @zydmayday as you're working on the Chinese translation for Vue in add new zh-CN folder for intro-to-storybook/vue and translate get-sta… #436 if you could adjust accordingly.
• @jeanphibaconnais as you're working on the French translation for the Vue edition (sorry for the radio silence but it was a bit intended as I wanted to push the tutorial for Vue 3 and Storybook 6.2, now that's stable).
• @IvanSotelo if you could as well take a look at the changes when they're merged we'd appreciate your updates to the Vue/Svelte editions.
• @katepark1009 and @jinho6225 if you could adjust the Korean translation when you're able we'd appreciate it.
• @Draketheb4dass if you could adjust the French translation and coordinate with @Dschungelabenteuer and @jeanphibaconnais it would be great.

Feel free to provide feedback

[jonniebigodes]

Self merging this

[jeanphi-baconnais]

Hi @jonniebigodes , for the french vue translatation, do you prefer i create a new PR or i continue on this existing one https://github.com/chromaui/learnstorybook.com/pull/434/commits

[jonniebigodes]

@jeanphibaconnais you can continue on your pull request. Fine by me, as you have already the bulk of the work done. In terms of changes for the Vue edition, it's only the snippets that require a bit of work and also some minor wording changes here and there. But if you want to open a fresh pull request I'm good with it as well. I'll let you decide.