Browse by/search for chord sets

[yaph]

Ideas:

• Index of songs with 1, 2, 3, 4, 5 or more than 5 chords.
• Index of songs with the "X Most Common Chord Sets", see https://ukealong.com/statistics/
• Add a filter to show only the selected chord sets on chord pages, above the list of songs on chord pages like https://ukealong.com/key/c/
• Search field that allows to enter several chord names and returns all songs that include those chords.
• Results should show the chords of the song next to the artist and title.