docs: Give examples of using other build.yaml props

build.yaml

@@ -1,14 +1,19 @@
-# This file generates the GitHub Actions matrix
-# For simple board + shield combinations, add them
-# to the top level board and shield arrays, for more
-# control, add individual board + shield combinations to
-# the `include` property, e.g:
+# This file generates the GitHub Actions matrix.
+# For simple board + shield combinations, add them to the top level board and
+# shield arrays, for more control, add individual board + shield combinations
+# to the `include` property. You can also use the `cmake-args` property to
+# pass flags to the build command and `artifact-name` to assign a name to
+# distinguish build outputs from each other:
 #
 # board: [ "nice_nano_v2" ]
 # shield: [ "corne_left", "corne_right" ]
 # include:
 #   - board: bdn9_rev2
 #   - board: nice_nano_v2
 #     shield: reviung41
+#   - board: nice_nano_v2
+#     shield: corne_left
+#     cmake-args: -DKEYMAP_FILE=../../config/alternate.keymap
+#     artifact-name: corne_alternate_left
 #
 ---