refactor: Add js-yaml dep, scrtipt gen tweaks.

*  Make the synthetic "base name" property double underscore prefixed,
  since internal, and to avoid future conflicts w/ YAML format add'ns.
* Switch to PS hash dictionaries for our metadata collections for saner
  data inspection/use.

docs/src/setup-script-generation-plugin/index.js

@@ -14,8 +14,8 @@ const Mustache = require("mustache");
 function generateSetupScripts() {
   return glob("../app/boards/**/*.zmk.yml", (error, files) => {
     const aggregated = files.map((f) => ({
-      ...yaml.safeLoadAll(fs.readFileSync(f, "utf8"))[0],
-      base_dir: path.basename(path.dirname(f)),
+      ...yaml.load(fs.readFileSync(f, "utf8")),
+      __base_dir: path.basename(path.dirname(f)),
     }));
 
     const data = aggregated.reduce(