Add configurable strict mode to itinerary filter

[amy-corson-ibigroup]

Description:

Adds support for a config item that will filter itineraries based on exactly what modes the user has selected (eliminates walk itineraries being shown by default if user did not specifically select a walk mode)

PR Checklist:

• [n/a] Does the code follow accessibility standards (WCAG 2.1 AA Compliant)?
• [n/a] Are all languages supported (Internationalization/Localization)?
• [n/a] Are appropriate Typescript types implemented?

@daniel-heppner-ibigroup also wrote this and I forgot to put him in the commit!!!

[miles-grant-ibigroup]

I think it could be helpful to have a larger discussion about what exactly we're doing here...

But in the meantime I have a few quick cleanup suggestions. Also, the new config item needs to go in the example config!

[miles-grant-ibigroup]

Looking much better! Could we possibly add comments to the rest of the new code? Since it is a little bit confusing

[miles-grant-ibigroup]

One last cleanup!

[miles-grant-ibigroup]

We're almost ready to go! We just need to get rid of that else block

[miles-grant-ibigroup]

We got there! Thanks for all your work on this

[AdrianaCeric]

Works great, nice job!