docs: clarify that Bake YAML support means Compose files (fixes #22759)

The overview and introduction pages described Bake as supporting "HCL,
JSON, or YAML formats", implying a standalone YAML bake file format
exists. Reworded to clarify that HCL and JSON are native Bake file
formats, while YAML support means Bake can build from a Compose file.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: dvdksn

content/manuals/build/bake/_index.md

@@ -10,9 +10,9 @@ Bake is a feature of Docker Buildx that lets you define your build configuration
 using a declarative file, as opposed to specifying a complex CLI expression. It
 also lets you run multiple builds concurrently with a single invocation.
 
-A Bake file can be written in HCL, JSON, or YAML formats, where the YAML format
-is an extension of a Docker Compose file. Here's an example Bake file in HCL
-format:
+A Bake file can be written in HCL or JSON format. Bake can also build directly
+from a [Docker Compose file](./compose-file.md). Here's an example Bake file in
+HCL format:
 
 ```hcl {title=docker-bake.hcl}
 group "default" {

content/manuals/build/bake/introduction.md

@@ -51,10 +51,11 @@ building images in a consistent way, with the same configuration.
 
 ## The Bake file format
 
-You can write Bake files in HCL, YAML (Docker Compose files), or JSON. In
-general, HCL is the most expressive and flexible format, which is why you'll
-see it used in most of the examples in this documentation, and in projects that
-use Bake.
+You can write Bake files in HCL or JSON. Bake can also read
+[Docker Compose files](./compose-file.md) and translate each service to a build
+target. HCL is the most expressive and flexible format, which is why you'll see
+it used in most of the examples in this documentation, and in projects that use
+Bake.
 
 The properties that can be set for a target closely resemble the CLI flags for
 `docker build`. For instance, consider the following `docker build` command: