add traveltimes to vignette

[AlexandraKapp]

extension of the vignette for the gtfs_traveltimes function.
I kept it quite basic. Any additions or futher explanations that should be included?

[mpadge]

Thanks @AlexandraKapp, but please see #55 first - I think this would be much better in it's own separate vignette. Could you please accordingly copy your code across to a new vignette file, and we'll start from there? Thanks!

[codecov]

Codecov Report

Merging #80 (a3c8d47) into main (b74a2b7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #80   +/-   ##
=======================================
  Coverage   87.84%   87.84%           
=======================================
  Files          19       19           
  Lines        1826     1826           
=======================================
  Hits         1604     1604           
  Misses        222      222           

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[mpadge]

Thanks for putting your name on it. Current version now fails because of new start_time_limits parameter which expects two values, and fails if there is only one, as in current code. Once you've updated that, I'll happily merge.

[AlexandraKapp]

now it should work :) feel free to edit or add content