DOCS improve registration in VueJs guide

[elevatebart]

Issue: #6357

What I did

Following issue #6357, I added a <details> section to the vue guide, to signal the need for global registration if the stories return plain text.

I added a JSX solution as well.

How to test

Read the docs on zeit

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[codecov]

Codecov Report

Merging #6608 into next will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             next    #6608      +/-   ##
==========================================
+ Coverage   40.57%   40.61%   +0.03%     
==========================================
  Files         637      633       -4     
  Lines        8714     8660      -54     
  Branches      625      620       -5     
==========================================
- Hits         3536     3517      -19     
+ Misses       5089     5054      -35     
  Partials       89       89

Impacted Files	Coverage Δ
addons/contexts/src/preview/libs/getPropsMap.ts	100% <0%> (ø)	⬆️
...ddons/contexts/src/preview/libs/getContextNodes.ts	100% <0%> (ø)	⬆️
lib/ui/src/components/sidebar/SidebarStories.js	100% <0%> (ø)	⬆️
addons/contexts/src/index.ts	0% <0%> (ø)	⬆️
...ddons/contexts/src/preview/libs/getRendererFrom.ts	100% <0%> (ø)	⬆️
lib/ui/src/components/sidebar/SidebarHeading.js	88.88% <0%> (ø)	⬆️
lib/components/src/tooltip/WithTooltip.tsx	25% <0%> (ø)	⬆️
addons/contexts/src/manager/libs/useChannel.ts	0% <0%> (ø)	⬆️
addons/knobs/src/components/types/Color.js	29.62% <0%> (ø)	⬆️
lib/ui/src/components/sidebar/SidebarItem.js	96% <0%> (ø)	⬆️
... and 21 more

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[shilman]

LGTM @elevatebart 👏

Made a few tweaks FYI:

• Edited the description Isuse: #xxx
• Added the patch label because it's a doc update that needs to get merged back into master to be deployed (if it was 5.1-specific docs I wouldn't add it)