chore: add non-implemented methods in Pulse class

So it can be subclassed.

Author: rwnobrega

src/komm/_pulses/Pulse.py

@@ -1,3 +1,8 @@
+from functools import cached_property
+
+import numpy as np
+import numpy.typing as npt
+
 from .. import abc
 
 
@@ -6,4 +11,23 @@ class Pulse(abc.Pulse):
     General pulse [Not implemented yet].
     """
 
-    pass
+    def waveform(self, t: npt.ArrayLike) -> npt.NDArray[np.floating]:
+        raise NotImplementedError
+
+    def spectrum(self, f: npt.ArrayLike) -> npt.NDArray[np.complexfloating]:
+        raise NotImplementedError
+
+    def autocorrelation(self, tau: npt.ArrayLike) -> npt.NDArray[np.floating]:
+        raise NotImplementedError
+
+    def energy_density_spectrum(self, f: npt.ArrayLike) -> npt.NDArray[np.floating]:
+        raise NotImplementedError
+
+    @cached_property
+    def support(self) -> tuple[float, float]:
+        raise NotImplementedError
+
+    def taps(
+        self, samples_per_symbol: int, span: tuple[int, int] | None = None
+    ) -> npt.NDArray[np.floating]:
+        return super().taps(samples_per_symbol, span)