Add type stubs for mido MIDI library

- Created type stubs for various modules in the mido library including messages, midifiles, parser, ports, sockets, syx, tokenizer, and version.
- Implemented type hints for functions and classes to improve type checking and code clarity.
- Added support for MIDI over TCP/IP in sockets module.
- Included methods for reading and writing SYX files in syx module.
- Enhanced the parser functionality with a dedicated Parser class for MIDI byte streams.
- Established a structure for MIDI file handling with MidiFile and MidiTrack classes.

typings/mido/midifiles/units.pyi

@@ -0,0 +1,38 @@
+from numbers import Real
+
+type _RealNumber = int | float | Real
+type _TimeSignature = tuple[int, int]
+
+def tick2second(tick: _RealNumber, ticks_per_beat: _RealNumber, tempo: _RealNumber) -> float:
+    """Convert absolute time in ticks to seconds.
+
+    Returns absolute time in seconds for a chosen MIDI file time resolution
+    (ticks/pulses per quarter note, also called PPQN) and tempo (microseconds
+    per quarter note).
+    """
+
+def second2tick(second: _RealNumber, ticks_per_beat: _RealNumber, tempo: _RealNumber) -> int:
+    """Convert absolute time in seconds to ticks.
+
+    Returns absolute time in ticks for a chosen MIDI file time resolution
+    (ticks/pulses per quarter note, also called PPQN) and tempo (microseconds
+    per quarter note). Normal rounding applies.
+    """
+
+def bpm2tempo(bpm: _RealNumber, time_signature: _TimeSignature = (4, 4)) -> int:
+    """Convert BPM (beats per minute) to MIDI file tempo (microseconds per
+    quarter note).
+
+    Depending on the chosen time signature a bar contains a different number of
+    beats. These beats are multiples/fractions of a quarter note, thus the
+    returned BPM depend on the time signature. Normal rounding applies.
+    """
+
+def tempo2bpm(tempo: _RealNumber, time_signature: _TimeSignature = (4, 4)) -> float:
+    """Convert MIDI file tempo (microseconds per quarter note) to BPM (beats
+    per minute).
+
+    Depending on the chosen time signature a bar contains a different number of
+    beats. The beats are multiples/fractions of a quarter note, thus the
+    returned tempo depends on the time signature denominator.
+    """