fix(ts): fix router.extendRoutes method type

[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

Fixes https://github.com/nuxt/nuxt.js/issues/5693

Credits

Co-authored-by: @renestalder

[codecov-io]

Codecov Report

Merging #5700 into dev will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##             dev   #5700   +/-   ##
=====================================
  Coverage   95.6%   95.6%           
=====================================
  Files         82      82           
  Lines       2664    2664           
  Branches     683     683           
=====================================
  Hits        2547    2547           
  Misses        98      98           
  Partials      19      19

---

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 6775024...42a470d. Read the comment docs.