Add Lowdefy to IDE/Tools

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- [x] Submit one item per pull request. This eases reviewing and speeds up inclusion.
- [x] Format your submission as follows, where `Demo` and `Clients` are optional.
  Do not add a duplicate `Source code` link if it is the same as the main link.
  Keep the short description under 250 characters and use [sentence case](https://en.wikipedia.org/wiki/Letter_case#Sentence_case)
  for it, even if the project's webpage or readme uses another capitalisation
  such as title case, all caps, small caps or all lowercase.
  ``- [Name](http://homepage/) - Short description, under 250 characters, sentence case. ([Demo](http://url.to/demo), [Source Code](http://url.of/source/code), [Clients](https://url.to/list/of/related/clients-or-apps)) `License` `Language` ``
- [ ] Additions that depend on proprietary services outside the user's control must be marked `⚠`.
  ``- [Name](http://homepage/) `⚠` - Short description, under 250 characters, sentence case. ([Demo](http://url.to/demo), [Source Code](http://url.of/source/code), [Clients](https://url.to/list/of/related/clients-or-apps)) `License` `Language` ``
- [ ] Additions that are not [Free software](https://en.wikipedia.org/wiki/Free_software)
  must be added to `non-free.md` and marked `⊘ Proprietary`:
  ``- [Name](http://homepage/) `⊘ Proprietary` - Short description, under 250 characters, sentence case. ([Demo](http://url.to/demo), [Source Code](http://url.of/source/code), [Clients](https://url.to/list/of/related/clients-or-apps)) `Language` ``
- [ ] Additions are inserted preserving alphabetical order.
- [ ] Additions are not already listed at any of
  - [awesome-sysadmin](https://github.com/n1trux/awesome-sysadmin) (IT infrastructure management),
  - [awesome-analytics](https://github.com/onurakpolat/awesome-analytics) (analytics),
  - [staticgen.com](https://www.staticgen.com/)
  - [staticsitegenerators.net](https://staticsitegenerators.net/) (static site generators).
- [ ] The `Language` tag is the main server-side requirement for the software - don't include frameworks or specific dialects.
- [ ] Any license you add is in our [list of licenses](https://github.com/awesome-selfhosted/awesome-selfhosted/blob/master/README.md#list-of-licenses).
- [ ] You have searched the repository for any relevant [issues](https://github.com/awesome-selfhosted/awesome-selfhosted/issues) or [PRs](https://github.com/awesome-selfhosted/awesome-selfhosted/pulls), including closed ones.
- [ ] Any category you are creating has the minimum requirement of 3 items.
  If not, your addition may be inserted into `Misc/Other`.
- [ ] Any software project you are adding to the list is actively maintained.
- [ ] The pull request title is informative, unlike "Update README.md".
  Suggested titles: "Add aaa to bbb" for adding software aaa to section bbb,
  "Remove aaa from bbb" for removing, "Fix license for aaa", etc.

README.md

@@ -1413,6 +1413,7 @@ _See [Ticketing](#ticketing)_
 - [JS Bin](http://jsbin.com/) - Open source collaborative web development debugging tool. ([Source Code](https://github.com/jsbin/jsbin)) `MIT` `Nodejs`
 - [Judge0 API](https://api.judge0.com) - Open source API to compile and run source code. ([Source Code](https://github.com/judge0/api)) `GPL-3.0` `Ruby`
 - [JupyterLab](http://jupyterlab.github.io/jupyterlab/) - Web-based environment for interactive and reproducible computing. ([Demo](https://mybinder.org/v2/gh/jupyterlab/jupyterlab-demo/try.jupyter.org?urlpath=lab), [Source Code](https://github.com/jupyterlab/jupyterlab/)) `BSD-3-Clause` `Python/Docker`
+- [Lowdefy](https://www.lowdefy.com/) - Build internal tools, BI dashboards, admin panels, CRUD apps and workflows in minutes using YAML / JSON on an self-hosted, open-source platform. Connect to your data sources, host via Serverless, Netlify or Docker. ([Source Code](https://github.com/lowdefy/lowdefy)) `Apache-2.0` `NodeJs`
 - [ML Workspace](https://github.com/ml-tooling/ml-workspace) - All-in-one web-based IDE for machine learning and data science. `Apache-2.0` `Docker`
 - [Regexr](http://regexr.com/) - RegExr is a HTML/JS based tool for creating, testing, and learning about Regular Expressions. ([Source Code](https://github.com/gskinner/regexr)) `MIT` `Nodejs`
 - [RequestBin](https://github.com/Runscope/requestbin) - Inspect HTTP requests. Debug webhooks. `MIT` `python`