update postBuild script

Author: DenisaCG

binder/environment.yml

@@ -17,6 +17,7 @@ dependencies:
   - nodejs >=18,<19
   - pip
   - wheel
+  # packages needed for build to succeed
   - certipy
   - async_generator
   # additional packages for demos

binder/postBuild

@@ -30,6 +30,8 @@ def _(*args, **kwargs):
 _(sys.executable, "-m", "pip", "check")
 
 # install the labextension
+_("jlpm", "install")
+_("jlpm", "build")
 _(sys.executable, "-m", "pip", "install", "-e", ".")
 _(sys.executable, "-m", "jupyter", "labextension", "develop", "--overwrite", ".")