fix(ts): Add missing loading property to Component options

[kevinmarrec]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

See :
https://nuxtjs.org/examples/custom-page-loading => about.vue
https://github.com/nuxt/nuxt.js/blob/dev/packages/vue-app/template/client.js#L388

This PR add missing typedefs and is also linked to missing documentation of the loading property in pages/components.

Todo

• Fix
• Documentation (en: Add docs for loading property docs#1111)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: en: Add docs for loading property docs#1111)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-io]

Codecov Report

Merging #4786 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #4786   +/-   ##
=======================================
  Coverage   90.82%   90.82%           
=======================================
  Files          67       67           
  Lines        2288     2288           
  Branches      569      569           
=======================================
  Hits         2078     2078           
  Misses        187      187           
  Partials       23       23

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update add233c...4cc235c. Read the comment docs.