The MarkdownLexer highlights **bold** and *italic* spans, but the combined bold-italics form ***bold italics*** (and ___bold italics___) was not recognized and fell through to plain Text:

>>> from pygments.lexers.markup import MarkdownLexer
>>> [(str(t), v) for t, v in MarkdownLexer().get_tokens('***bold italics***') if v.strip()]
[('Token.Text', '***bold'), ('Token.Text', 'italics***')]

Pygments already has a dedicated Generic.EmphStrong token for exactly this case, so this adds two inline rules that emit it. They are placed before the existing **/__ bold rules so the triple markers aren't partially consumed.

After:

>>> [(str(t), v) for t, v in MarkdownLexer().get_tokens('***bold italics***') if v.strip()]
[('Token.Generic.EmphStrong', '***bold italics***')]

Existing **bold**, __bold__, *italic*, _italic_ and the snake***case***word non-emphasis behavior are unchanged.

Tests

Extended tests/examplefiles/md/example.md with bold-italics lines (both the emphasized form and the snake***case***word non-match) and regenerated the golden output. pytest tests/examplefiles/md/ tests/test_basic_api.py passes (2446 passed, 8 skipped).

Closes #3067