Fixed typos in docstring and comment in README.rst and fourigui.py

Author: Filippo Ballerini

README.rst

@@ -122,7 +122,7 @@ trying to commit again.
 
 Improvements and fixes are always appreciated.
 
-Before contribuing, please read our `Code of Conduct <https://github.com/diffpy/diffpy.fourigui/blob/main/CODE_OF_CONDUCT.rst>`_.
+Before contributing, please read our `Code of Conduct <https://github.com/diffpy/diffpy.fourigui/blob/main/CODE_OF_CONDUCT.rst>`_.
 
 Contact
 -------

src/diffpy/fourigui/fourigui.py

@@ -461,7 +461,7 @@ def applycutoff(self):
         reassign all voxels with distance smaller than qmin and greater than qmax
         from the central voxel to 0.0
         qmin, qmax is loaded from the qmin, qmax input panel
-        currently opperates in units of pixels
+        currently operates in units of pixels
         """
         if not self.cutted: