Find nearest evac routes / case 1 polygon intersect point to user

When user enters an address or uses geolocation, find nearest intersection between Evac Routes and Case 1 Polygon using pre-calculated [intersect points](https://github.com/HighGroundAlert/high-ground-alert/blob/01af329dea2ff425ab117784e28edde679e06fba/evac_rtes_case1_intersect_pts_wgs84.json).
Show this point to the user as a potential safe place to go.
