Reconsider .help-block styles

[gadenbuie]

bslib includes BS3 backwards compat styles for the .help-block class used by helpText():

.help-text, .help-block {
  @extend .form-text; @extend .text-muted;
}

But in BS3, .help-block included display: block (hence the -block suffix). We don't have similar styles in BS4+, so helpText() renders inline instead of below the controls it tries to describe.

BS3	BS5

Example shinylive app

Two options:

1. Add a .help-block class to BS4+ that includes display: block.
2. helpText() might be due for an update.