using colors - easier way

[danielb2]

Before, this code worked to change the indent color using vim syntax (vs lua)

hi BLIndent1 guifg=#222222
lua require('indent_blankline').setup({ char_highlight_list = { "BLIndent1" } })

the current readme is quite confusing with hooks etc, but this is what I did to get it working with v3

hi BLIndent1 guifg=#222222
lua require("ibl").setup({ indent = { highlight = "BLIndent1" } })

maybe this will help someone. also, maybe you can include this in the readme as it's a lot easier than the examples you have there now