Add links to Next Train API and Mobile Apps

[s2t2]

Hi, thanks for maintaining this list. I've added some links to apps I have created that I'm hoping others will find valuable.

[barbeau]

Thanks @s2t2 for submitting this! A few comments/questions inline.

[s2t2]

Hi @barbeau please see my revision and comments.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ carlfredl
❌ s2t2
_{You have signed the CLA already but the status is still pending? Let us recheck it.}