[GRASS-git] [OSGeo/grass] b87fec: Update alpine version in Dockerfile (#2073)

[Carmen Tawalika]

  Branch: refs/heads/main
  Home:   https://github.com/OSGeo/grass
  Commit: b87fece301fd2c051c8abb991bd5a4654e67157f
      https://github.com/OSGeo/grass/commit/b87fece301fd2c051c8abb991bd5a4654e67157f
  Author: Carmen Tawalika <mmacata at users.noreply.github.com>
  Date:   2022-03-30 (Wed, 30 Mar 2022)

  Changed paths:
    M docker/alpine/Dockerfile

  Log Message:
  -----------
  Update alpine version in Dockerfile (#2073)

* update alpine version from 3.12 to 3.15
* update extensions (more fixes forthcoming in a new PR)
* add PROJ_NETWORK env to avoid inclusion of huge proj-data files.