docs: import version and specification version from sigmf

Rather than parsing __init__.py, import the Python module and grab
the values from there. This should work as long as sigmf-python is
installed in the venv used to build the docs.

Author: daniestevez

docs/source/conf.py

@@ -10,13 +10,10 @@
 import sys
 from pathlib import Path
 
-# parse info from project files
+import sigmf
 
-root = Path(__file__).parent.parent.parent
-with open(root / "sigmf" / "__init__.py", "r") as handle:
-    init = handle.read()
-    toolversion = re.search(r'__version__\s*=\s*[\'"]([^\'"]*)[\'"]', init).group(1)
-    specversion = re.search(r'__specification__\s*=\s*[\'"]([^\'"]*)[\'"]', init).group(1)
+toolversion = sigmf.__version__
+specversion = sigmf.__specification__
 
 # autodoc needs special pathing
 sys.path.append(str(root))
@@ -68,4 +65,4 @@
 ]
 frozen_locals = dict(locals())
 rst_epilog = '\n'.join(map(lambda x: f".. |{x}| replace:: {frozen_locals[x]}", variables_to_export))
-del frozen_locals
+del frozen_locals