bug(adoc): validation pattern is rendered in bold when containing asteriskes

[tenstad]

[a-z]*-[a-z]* is rendered as -[a-z] (bold)

Should look into escaping the asterix

[tenstad]

In the GitLab renderer, it appears every other asterix should be escaped 🤔

Pattern: `[a]\*[b]\*[c]\*[d][a]\*[b]\*[c]\*[d]` +
Pattern: `[a]\*[b]*[c]\*[d][a]*[b]\*[c]*[d]` +
Pattern: `[a]*[b]*[c]*[d][a]*[b]*[c]*[d]` +

Pattern: [a]*[b]\*[c]*[d][a]\*[b]*[c]\*[d]
Pattern: [a]*[b]*[c]*[d][a]*[b]*[c]*[d]
Pattern: [b][c][d][a][b][c][d]

Which matches the example in https://docs.asciidoctor.org/asciidoc/latest/subs/prevent/#escape-with-backslashes