gh-105096: Reformat wave documentation (#105136)

Add ".. class::" markups in the wave documentation.

* Reformat also wave.py (minor PEP 8 changes).
* Remove redundant "import struct": it's already imported at top
  level.
* Remove wave.rst from .nitignore

Lib/wave.py

@@ -92,6 +92,7 @@ _array_fmts = None, 'b', 'h', None, 'i'
 _wave_params = namedtuple('_wave_params',
                      'nchannels sampwidth framerate nframes comptype compname')
 
+
 def _byteswap(data, width):
     swapped_data = bytearray(len(data))
 
@@ -104,7 +105,6 @@ def _byteswap(data, width):
 
 class _Chunk:
     def __init__(self, file, align=True, bigendian=True, inclheader=False):
-        import struct
         self.closed = False
         self.align = align      # whether to align to word (2-byte) boundaries
         if bigendian:
@@ -214,7 +214,6 @@ class _Chunk:
                 raise EOFError
 
 
-
 class Wave_read:
     """Variables used in this class:
 
@@ -411,6 +410,7 @@ class Wave_read:
         self._comptype = 'NONE'
         self._compname = 'not compressed'
 
+
 class Wave_write:
     """Variables used in this class:
 
@@ -638,6 +638,7 @@ class Wave_write:
         self._file.seek(curpos, 0)
         self._datalength = self._datawritten
 
+
 def open(f, mode=None):
     if mode is None:
         if hasattr(f, 'mode'):