Add support for cljc files (#1096)

fixes #1097 

I'm not sure if this is the extent of changes that need to occur, but
I've been using these changes locally to start porting
[portal](https://github.com/djblue/portal) and it's been working for me.

Author: djblue

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Added
  * Added support for Python 3.13 (#1056)
+ * Added support for `.cljc` files (#1097)
 
 ### Fixed
  * Fix an issue with `basilisp test` standard streams output that can lead to failures on MS-Windows (#1080)

src/basilisp/importer.py

@@ -105,7 +105,7 @@ def _is_package(path: str) -> bool:
     or Python code file."""
     for _, _, files in os.walk(path):
         for file in files:
-            if file.endswith(".lpy") or file.endswith(".py"):
+            if file.endswith(".lpy") or file.endswith(".py") or file.endswith(".cljc"):
                 return True
     return False
 
@@ -122,7 +122,7 @@ def _is_namespace_package(path: str) -> bool:
     for file in files:
         if file in {"__init__.lpy", "__init__.py"}:
             no_inits = False
-        elif file.endswith(".lpy"):
+        elif file.endswith(".lpy") or file.endswith(".cljc"):
             has_basilisp_files = True
     return no_inits and has_basilisp_files
 
@@ -161,6 +161,8 @@ def find_spec(
             filenames = [
                 f"{os.path.join(root_path, '__init__')}.lpy",
                 f"{root_path}.lpy",
+                f"{os.path.join(root_path, '__init__')}.cljc",
+                f"{root_path}.cljc",
             ]
             for filename in filenames:
                 if os.path.isfile(filename):