chore: clean build.yml, make matrix more visible

there were huge blocks of good documentation,
but it was in the way of easy access to the matrix section,
 which ordinary users have to update

 it was also only about build triggers, which is a pretty clear topic
 much more valuable would be explaining each build step

 i condesensed the docs into a smaller section atop
 with only generally useful information

.github/workflows/build.yml

@@ -1,33 +1,17 @@
+# This workflow builds every branch of the repository daily at 20:22 UTC, one hour after ublue-os/nvidia builds.
+# The images are also built after pushuing changes or pull requests.
+# The builds can also be triggered manually in the Actions tab thanks to workflow dispatch. 
+# Only the branch called `live` is published.
+
+
 name: build-ublue
-on:
-  # Build *every* branch at 10:20pm UTC every day (1 hr delay after "nvidia" builds),
-  # regardless of the branch names. (Not just "live, template and main" branches.)
-  # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#schedule
+on: # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows
   schedule:
     - cron: "20 22 * * *"
-  # Build automatically after pushing commits or tags to the "live", "template"
-  # or "main" branches, except when the commit only affects "documentation" text files.
-  # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#push
   push:
-    branches:
-      - live
-      - template
-      - main
-    paths-ignore:
+    paths-ignore: # don't rebuild if only documentation has changed
       - "**.md"
-      - "**.txt"
-  # Build pull requests whenever they are opened or updated, to make sure they
-  # work. The build won't be deployed, since we filter out PRs in the deployment
-  # stage. Note that submitted PRs run the workflow of the *fork's* own primary
-  # branch, using the fork's own secrets/environment. Please be sure to sync
-  # your primary branch with upstream's latest workflow before submitting PRs!
-  # For pull requests, we build *any* branch regardless of name, to allow "build
-  # checks" to succeed for typical PR branch names such as "fix-something".
-  # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request
   pull_request:
-  # Build when manually triggering this workflow for a branch. This allows you
-  # to build any branch, even if it's not listed in the automated triggers above.
-  # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_dispatch
   workflow_dispatch:
 
 env:
@@ -47,10 +31,12 @@ jobs:
       fail-fast: false
 
       matrix:
+# !!!
         # Add recipes for all the images you want to build here.
         # Don't add module configuration files, you will get errors.
         recipe:
           - recipe.yml
+# !!!
 
     steps:
       # Checkout push-to-registry action GitHub repository