Add .sticky-thead for sticky table headers on scroll

[mdo]

• Replaces Added a class for a new feature to fix table header on top #29456
• Fixes Thead Fixed #35998
• Fixes Feature request: Scrollable table body with fixed header #13058, fixes Consider adding class table-fixedheader #12780, fixes Static <thead> on Long Tables #1804 (lol)

[louismaximepiton]

We tried to add:

  > * > th {
    $border-bottom-thead: subtract(100%, ($table-border-width * 2));
    background: linear-gradient(transparent 0%, transparent $border-bottom-thead, var(--#{$prefix}table-border-color) $border-bottom-thead, var(--#{$prefix}table-border-color) 100%);
    background-color: var(--#{$prefix}table-bg);
  }

to "redraw" the separator between thead and tbody, I don't know if this could be useful here (instead of having a utility to change bg)(preview)?

[AgentSmith0]

What speaks against merging this?

[piskesocute]

@mdo When can this merge be approved?

[julien-deramond]

Just FYI, I've rebased and resolved the conflicts for this branch so that it's ready to be reviewed.

What speaks against merging this?

When can this merge be approved?

For now, it's planned for the v5.4 as it's a new feature, and we're currently working on some patches for v5.3.x.

[leefordjudes]

Kindly add this feature, i need it for my project,
that is fixed table header and scrollable table body.