Restore findOwnPaths for serve_index.html in build module

Move serve_index.html to cli-module-build/templates and use
findOwnPaths instead of require.resolve for safer path resolution.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

packages/cli-module-build/package.json

@@ -19,9 +19,11 @@
   "license": "Apache-2.0",
   "main": "src/index.ts",
   "types": "src/index.ts",
+  "bin": "bin/cli-module-build",
   "files": [
     "dist",
-    "bin"
+    "bin",
+    "templates"
   ],
   "scripts": {
     "build": "backstage-cli package build",
@@ -98,6 +100,5 @@
     "@types/lodash": "^4.14.151",
     "@types/npm-packlist": "^3.0.0",
     "@types/shell-quote": "^1.7.5"
-  },
-  "bin": "bin/cli-module-build"
+  }
 }