feat(__main__.py): add support for rajini++ shell

rajini++ shell allows you to run rajini++ statements line by line on the terminal.

rajinipp/__main__.py

@@ -1,6 +1,8 @@
+import pdb
+
 from typer import Typer
 
-from . import __version_str__
+from . import __version__, __version_str__
 from .runner import RppRunner
 
 app = Typer()
@@ -32,6 +34,16 @@ def run(file_path: str, debug: bool = False):
     runner.exec(code=code_str, log_level=level)
 
 
+@app.command()
+def shell():
+    print(f"rajini++ v{__version__}")
+    while True:
+        code_line = input("rajinipp>> ")
+        output = runner.eval(code_line)
+        if output:
+            print(output)
+
+
 @app.callback()
 def main():
     """