brookmd 0.30.1 — No more React nesting warnings on tables

No more React nesting warnings on tables. A React-only fix; brookmd-core
stays at 0.27.0 and the wire contract is unchanged.

Fixed

• Whitespace text under table structure. The core serializes tables one
  tag per line (<table>\n<thead>\n<tr>\n…). When a table went through the
  React element walker — any urlTransform, tag-level components override,
  or decorators, and brookmd/server/react with components — those newlines became text
  children of <table>/<thead>/<tbody>/<tfoot>/<tr>, which React
  rejects (validateDOMNesting: Whitespace text nodes cannot appear as a child of <tr>). The walker now drops text that is purely ASCII HTML
  whitespace when its direct parent is one of those tags or <colgroup>.
  Cell content, <pre>/<code> inside cells, non-breaking and other
  Unicode spaces, and non-whitespace stray text are all kept, and
  parseTrustedHtml still returns every text node. Plain rendering (no
  transforms), streaming tables with blockData, and the DOM, element, Vue,
  Svelte and Solid renderers were never affected. React Native already
  filtered these nodes. Thanks to @ethanfann for the report and the fix.