Feature : Adding countdown for hike screen and exit pop up box upon ending

**Is your feature request related to a problem? Please describe.**
There is no countdown on the hike screen for how long a hike is active.

**Describe the solution you'd like**
Add a countdown timer instead of the time of expiry on the hike screen. Also, add a pop-up box asking the user to return home as the beacon has expired.

**Additional context**
Any other suggestions or changes are open for discussion.

**Are you working on this? (Yes/No)**
Yes