Added eightfold.

[rl2939]

Added the eightfold modules.

[rl2939]

How do I fix the build error that the checks are complaining about (below)? It builds without error on my machine.

eightfold/src/SDOrcasHeartV2.cpp:320:33: error: 'constexpr rack::dsp::TSchmittTrigger<float>::<unnamed union>::<constructor>()' is inaccessible within this context
  320 |     dsp::SchmittTrigger clockIn{}, resetIn{}, scaleSwitchTrig{}, scaleInputTrig{};
      |                                 ^
In file included from /__w/Cardinal/Cardinal/src/Rack/include/rack.hpp:122,
                 from eightfold/src/plugin.hpp:1,
                 from eightfold/src/SDOrcasHeartV2.cpp:1:
/__w/Cardinal/Cardinal/src/Rack/include/dsp/digital.hpp:89:8: note: declared here
   89 |  union {
      |        ^
eightfold/src/SDOrcasHeartV2.cpp:320:44: error: 'constexpr rack::dsp::TSchmittTrigger<float>::<unnamed union>::<constructor>()' is inaccessible within this context
  320 |     dsp::SchmittTrigger clockIn{}, resetIn{}, scaleSwitchTrig{}, scaleInputTrig{};
      |                                            ^
In file included from /__w/Cardinal/Cardinal/src/Rack/include/rack.hpp:122,
                 from eightfold/src/plugin.hpp:1,
                 from eightfold/src/SDOrcasHeartV2.cpp:1:
/__w/Cardinal/Cardinal/src/Rack/include/dsp/digital.hpp:89:8: note: declared here
   89 |  union {
      |        ^
eightfold/src/SDOrcasHeartV2.cpp:320:63: error: 'constexpr rack::dsp::TSchmittTrigger<float>::<unnamed union>::<constructor>()' is inaccessible within this context
  320 |     dsp::SchmittTrigger clockIn{}, resetIn{}, scaleSwitchTrig{}, scaleInputTrig{};
      |                                                               ^
In file included from /__w/Cardinal/Cardinal/src/Rack/include/rack.hpp:122,
                 from eightfold/src/plugin.hpp:1,
                 from eightfold/src/SDOrcasHeartV2.cpp:1:
/__w/Cardinal/Cardinal/src/Rack/include/dsp/digital.hpp:89:8: note: declared here
   89 |  union {
      |        ^
eightfold/src/SDOrcasHeartV2.cpp:320:81: error: 'constexpr rack::dsp::TSchmittTrigger<float>::<unnamed union>::<constructor>()' is inaccessible within this context
  320 |     dsp::SchmittTrigger clockIn{}, resetIn{}, scaleSwitchTrig{}, scaleInputTrig{};
      |                                                                                 ^
In file included from /__w/Cardinal/Cardinal/src/Rack/include/rack.hpp:122,
                 from eightfold/src/plugin.hpp:1,
                 from eightfold/src/SDOrcasHeartV2.cpp:1:
/__w/Cardinal/Cardinal/src/Rack/include/dsp/digital.hpp:89:8: note: declared here
   89 |  union {
      |        ^
make[1]: *** [Makefile:2365: ../build/plugins/eightfold/src/SDOrcasHeartV2.cpp.o] Error 1

[falkTX]

maybe this needs c++17 too?