Add note about shell escaping

docs/documentation.html

@@ -746,12 +746,13 @@ <h3 id="importing-external-rules">Importing External Rules</h3>
        grammar, NOT the source.  Grammars MUST be compiled by a version that
        supports imports in order to be imported.  Only rules that are allowed
        start rules are valid.  It can be useful to specify
-       <code>--allowed-start-rules *</code> in library grammars.  Imports are
-       only valid in output formats "es" and "commonjs".  If you
-       use imports, you should use <code>{ output: "source" }</code>; the default
-       output of "parser" will call `eval` on the source which fails immediately
-       for some formats (e.g. "es") and will not find modules in the expected
-       places for others (e.g. "commonjs").  The
+       <code>--allowed-start-rules *</code> (with appropriate escaping for
+       your shell!) in library grammars.  Imports are only valid in output
+       formats "es" and "commonjs".  If you use imports, you should use
+       <code>{ output: "source" }</code>; the default output of "parser" will
+       call `eval` on the source which fails immediately for some formats
+       (e.g. "es") and will not find modules in the expected places for others
+       (e.g. "commonjs").  The
        <a href="https://github.com/peggyjs/from-mem/">from-mem</a> project is
        used by the Peggy CLI to resolve these issues, but note well its
        relatively severe limitations.</p>