Add SPA UI for GARM

This change adds a single page application front-end to GARM. It uses
a generated REST client, built from the swagger definitions, the websocket
interface for live updates of entities and eager loading of everything
except runners, as users may have many runners and we don't want to load
hundreds of runners in memory.

Proper pagination should be implemented in the API, in future commits,
to avoid loading lots of elements for no reason.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

README.md

@@ -18,6 +18,7 @@
         - [Installing on Kubernetes](#installing-on-kubernetes)
     - [Configuring GARM for GHES](#configuring-garm-for-ghes)
     - [Configuring GARM for Gitea](#configuring-garm-for-gitea)
+    - [Enabling the web UI](#enabling-the-web-ui)
     - [Using GARM](#using-garm)
     - [Supported providers](#supported-providers)
         - [Installing external providers](#installing-external-providers)
@@ -78,6 +79,17 @@ GARM supports creating pools and scale sets in either GitHub itself or in your o
 
 GARM now has support for Gitea (>=1.24.0). For information on getting started with Gitea, see the [Gitea quickstart](/doc/gitea.md) document.
 
+## Enabling the web UI
+
+GARM now ships with a single page application. To enable it, add the following to your GARM config:
+
+```toml
+[apiserver.webui]
+  enable = true
+```
+
+Check the [README.md](/webapp/README.md) file for details on the web UI.
+
 ## Using GARM
 
 GARM is designed with simplicity in mind. At least we try to keep it as simple as possible. We're aware that adding a new tool in your workflow can be painful, especially when you already have to deal with so many. The cognitive load for OPS has reached a level where it feels overwhelming at times to even wrap your head around a new tool. As such, we believe that tools should be simple, should take no more than a few hours to understand and set up and if you absolutely need to interact with the tool, it should be as intuitive as possible. Although we try our best to make this happen, we're aware that GARM has some rough edges, especially for new users. If you encounter issues or feel like the setup process was too complicated, please let us know. We're always looking to improve the user experience.