docs: Add experimental section w/bootc image

Let's follow a standard operating procedure for our experimental features:

- A github tracking issue
- A documentation section like this one

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

docs/src/SUMMARY.md

@@ -44,6 +44,10 @@
 - [Filesystem: sysroot](filesystem-sysroot.md)
 - [Container storage](filesystem-storage.md)
 
+# Experimental features
+
+- [bootc image](experimental-bootc-image.md)
+
 # More information
 
 - [Package manager integration](package-managers.md)

docs/src/experimental-bootc-image.md

@@ -0,0 +1,28 @@
+# bootc image
+
+Experimental features are subject to change or removal. Please
+do provide feedback on them.
+
+Tracking issue: <https://github.com/containers/bootc/issues/690>
+
+## Using `bootc image copy-to-storage`
+
+This experimental command is intended to aid in [booting local builds](booting-local-builds.md).
+
+Invoking this command will default to copying the booted container image into the `containers-storage:`
+area as used by e.g. `podman`, under the image tag `localhost/bootc` by default. It can
+then be managed independently; used as a base image, pushed to a registry, etc.
+
+Run `bootc image copy-to-storage --help` for more options.
+
+Example workflow:
+
+```
+$ bootc image copy-to-storage
+$ cat Containerfile
+FROM localhost/bootc
+...
+$ podman build -t localhost/bootc-custom .
+$ bootc switch --transport containers-storage localhost/bootc-custom
+```
+