Fixes for Teensy LC

Fix documentation for SGTL lineInLevel (swap channels)

Update index.html

Band limited waveforms

MQS: Play nice

keeps 352kHZ PWM, but reduces hardware-oversampling to 32x

changed
{"type":"AudioOutputPWM",        "resource":"DAC1",           "shareable":false},
to
{"type":"AudioOutputPWM",        "resource":"PWM",           "shareable":false},

Needed for Blocksize=128.
Blocksize 128 is needed for the waveplayer

PT8211: fix beep on startup

https://forum.pjrc.com/threads/64592-Teensyduino-1-54-Beta-5?p=263595&viewfull=1#post263595

wav2sketch - Update for T4.x

Update effect_rectifier.cpp

Bug: was overwriting a read-only buffer

Minor gui text updates

Replace the text formula with a png graphic generated from some
LaTeX source.
Formulas in HTML apparently never made it in the mainstream,
and the recommendation is to use LaTex to generate images. See:
https://www.w3.org/MarkUp/HTMLPlus/htmlplus_45.html

To convert the .tex to a png, try:
  pdflatex formulas.tex
  convert -density 300 formulas.pdf -quality 95 formulas.png

Signed-off-by: Graham Whaley <graham.whaley@gmail.com>

Note in the GUI help text that the ToneDetect uses the
Goertzel algorithm.

Signed-off-by: Graham Whaley <graham.whaley@gmail.com>

https://forum.pjrc.com/threads/64388-PT8211-and-Teensy-4?p=259415&viewfull=1#post259415

using the spdif configuration of AudioOutputSPDIF3 and more

Fix discontinuity in frequency stepping in tonesweep