Add Shelf

[KieronWiltshire]

Thanks for taking the time to suggest an addition to awesome-selfhosted!

Please fill out information below (all fields are mandatory unless noted otherwise):

# software name
name: "Shelf"
# URL of the software project's homepage
website_url: "https://www.shelf.nu/"
# URL where the full source code of the program can be downloaded
source_code_url: "https://github.com/Shelf-nu/shelf.nu"
# description of what the software does, shorter than 250 characters, sentence case
description: "Asset and Equipment tracking software used by teams who value clarity. Shelf is an asset database and QR asset label generator that lets you create, manage and overview your assets across locations."
# list of license identifiers, see https://github.com/awesome-selfhosted/awesome-selfhosted-data/blob/master/licenses.yml for the full list of licenses
licenses:
  - GNU Affero General Public License v3.0
# list of languages/platforms, see https://github.com/awesome-selfhosted/awesome-selfhosted-data/tree/master/platforms for the full list of platforms
platforms:
  - Nodejs
  - Docker
# list of tags (categories), see https://github.com/awesome-selfhosted/awesome-selfhosted-data/tree/master/tags for the full list of tags
tags:
  - Inventory Management
# (optional, yes/no, default no) whether the software depends on a third-party service outside the user's control
depends_3rdparty: no
# (optional) link to an interactive demo of the software
demo_url: "https://www.shelf.nu/demo"
# (optional) link to a list of clients/addons/plugins/apps/bots... for the software
related_software_url: ""

To ensure your issue is dealt with swiftly, please check the following (check the boxes [x]):

• Submit one item per pull issue. This eases reviewing and speeds up inclusion.
• You have searched the repository for any relevant issues or PRs, including closed ones.
• Any software you are adding is not already listed at any of awesome-sysadmin, staticgen.com, staticsitegenerators.net, dbdb.io.
• Any software project you are adding to the list is actively maintained.
• Any software project you are adding was first released more than 4 months ago.
• Any software project you are adding has working installation instructions.
• If you are adding software forked from another active project, please provide/link to a clear list of differences between both.

[Ki-er]

First release was July, meaning it does not meet the 4 months requirement.