[Docs] Document webpack in install steps

docs/admin/10_install.rst

@@ -143,6 +143,8 @@ After that, you can install the aleksis meta-package, or only `aleksis-core`:
 .. code-block:: shell
    pip3 install aleksis
    aleksis-admin yarn install
+   aleksis-admin write_webpack_entrypoints
+   yarn run webpack
    aleksis-admin collectstatic
    aleksis-admin migrate
    aleksis-admin createinitialrevisions