message: fix waveform docs link in the description
diff: <tone-explanation label="Analyser">
  <a href="https://tonejs.github.io/docs/FFT" target="_blank">Tone.FFT</a>
  returns the amplitude of the incoming signal at different frequencies.
  - <a href="https://tonejs.github.io/docs/FFT" target="_blank">Tone.Waveform</a>
  + <a href="https://tonejs.github.io/docs/Waveform" target="_blank">Tone.Waveform</a>
  returns the signal value between 0-1.
  </tone-explanation>
  