Accessibility: Improvements and suggestions

I identified several areas in the app where accessibility can be improved. I put more details in this google doc, which you should have access to with this [link](https://docs.google.com/document/d/1Lo1GbzK4xPWvlN2yvYriCjY-OaYF-LQ6lheIyI3DPpY/edit).

- [ ] Dynamic Text Size needs to be supported throughout the app, the only place I saw support for it was in the navigation bar.
- [ ] When reading over a podcast episode with VoiceOver it reads the `m` in `2m` as meters instead of minutes. I believe this may be fixed when I run it from Xcode but want to make sure it ships this way. Also, suggest changing the `m` to min so it is clearer to say that it's minutes instead of meters.


- [x] On the Discover Tab the plus button for adding a subscription is shown as “Discover add”, which sounds like an internal name for the button. This should say subscribe like the plus button like the other podcasts that are being shown on this page.


Start by reviewing the linked Google document and the remaining unchecked items. Trace the Dynamic Text Size support beyond the navigation bar, then inspect the podcast episode VoiceOver reading of durations such as “2m.” Done means the app supports the requested text sizing and presents the duration unambiguously to VoiceOver; the Discover Tab item is already checked.

Written by the indexing model from the issue text.