threejs feature: include version file in sage.feature

This makes the feature complete when only sagemath_environment is
installed.

Fixes: sagemath#37178

Author: tornaria

pkgs/sagemath-environment/pyproject.toml.m4

@@ -56,7 +56,6 @@ script-files = [
     # - bin/sage-run, bin/sage-runtests, ... -- installed by sagemath-repl
     # - bin/sage-ipython  -- uses sage.repl, so installed by sagemath-repl
 ]
-include-package-data = false
 
 [tool.setuptools.dynamic]
 version = {file = ["VERSION.txt"]}

src/sage/ext_data/threejs/threejs-version.txt renamed to src/sage/features/threejs-version.txt

@@ -52,9 +52,9 @@ def required_version(self):
             sage: Threejs().required_version()
             'r...'
         """
-        from sage.env import SAGE_EXTCODE
+        from importlib.resources import files
 
-        filename = os.path.join(SAGE_EXTCODE, 'threejs', 'threejs-version.txt')
+        filename = files(__package__).joinpath("threejs-version.txt")
 
         with open(filename) as f:
             return f.read().strip()