WarpSQL: Add PostGIS Extension

[jayanth-kumar-morem]

WarpSQL, WarpSQL/bitnami: Add PostGIS extension to PostgreSQL

WarpSQL:

1. Specify POSTGIS_MAJOR, PG_MAJOR, and POSTGIS_VERSION arguments
2. Update and install necessary dependencies
3. Add PostgreSQL repository and import key
4. Install PostGIS extension with specified versions
5. Clean up apt lists

WarpSQL/bitnami:

1. Implement ARGs for POSTGIS_VERSION and POSTGIS_SHA256 to support different PostGIS versions
2. Conditionally set environment variables GEOS_ALPINE_VER, GDAL_ALPINE_VER, and PROJ_ALPINE_VER based on the selected PostGIS version
3. Add Alpine repositories for required packages when using PostGIS 2.x

Fixes: #4

[ChakshuGautam]

https://github.com/all-contributors please add @jayanth-kumar-morem for Code.