add chord references

src/testdata/fifth_wheel.txt

@@ -0,0 +1,5 @@
+# fifth wheel = :shrug:
+# f -> c -> g -> d -> a -> e -> b
+
+f c g d a e b
+

src/testdata/major_chords.txt

@@ -0,0 +1,27 @@
+# major CHORD = root + major_third + perfect_fifth
+# c = c,e,g
+
+f
+a
+c
+
+c
+e
+g
+
+g
+b
+d
+
+d
+f+
+a
+
+a
+c+
+e
+
+e
+g+
+b
+

src/testdata/major_third.txt

@@ -0,0 +1,18 @@
+# major third
+# +2 letters (the third letter) with exactly 2 sharps between
+
+# c,e c+,f d,f+
+c c+ d
+e f  f+
+
+# d+,g e,g+ f,a
+d+ e  f
+g  g+ a
+
+# f+,a+ g,b g+,c
+f+ g g+
+a+ b c
+
+# a,c+ a+,d b,d+
+a  a+ b
+c+ d  d+

src/testdata/minor_chords.txt

@@ -0,0 +1,27 @@
+# minor CHORD = root + minor_third + perfect_fifth
+# c = c,e-,g
+
+f
+g+
+c
+
+c
+e-
+g
+
+g
+a+
+d
+
+d
+f
+a
+
+a
+c
+e
+
+e
+g
+b
+

src/testdata/minor_third.txt

@@ -0,0 +1,18 @@
+# minor third
+# +2 letters (the third letter) with exactly 1 half step between
+
+# c,e- c+,e d,f
+c  c+ d
+e- e  f
+
+# d+,f+ e,g f,g+
+d+ e  f
+f+ g  g+
+
+# f+,a g,a+ g+,b
+f+ g  g+
+a  a+ b
+
+# a,c a+,c+ b,d
+a  a+ b
+c  c+ d