add nightly tag from their repos

jenkins-vars.yml

@@ -2,14 +2,12 @@
 
 # jenkins variables
 project_name: docker-jellyfin
-external_type: github_stable
-release_type: stable
-release_tag: latest
-ls_branch: master
+external_type: na
+custom_version_command: "curl -sX GET https://repo.jellyfin.org/ubuntu/dists/bionic/main/binary-amd64/Packages |grep -A 7 -m 1 'Package: jellyfin-nightly' | awk -F ': ' '/Version/{print $2;exit}'"
+release_type: prerelease
+release_tag: nightly
+ls_branch: nightly
 repo_vars:
-  - EXT_GIT_BRANCH = 'master'
-  - EXT_USER = 'jellyfin'
-  - EXT_REPO = 'jellyfin'
   - BUILD_VERSION_ARG = 'JELLYFIN_RELEASE'
   - LS_USER = 'linuxserver'
   - LS_REPO = 'docker-jellyfin'