The marks come from the simple-icons package (CC0) and are inlined at build
time — the earlier hand-drawn glyphs were wrong, the X mark in particular is
not a plain cross. Importing the three SVGs individually rather than the
package index keeps the other icons out of the bundle: 10 kB, not 5 MB.
Rendered monochrome in the surrounding text colour, with the text label kept
next to each one.
