trimModuleSpecifierPrefix = (moduleSpecifier, prefix) => {
  if (moduleSpecifier === prefix) {
    return '.';
  }
  if (moduleSpecifier.startsWith(`${prefix}/`)) {
    return `./${moduleSpecifier.slice(prefix.length + 1)}`;
  }
  return undefined;
}
For a full, absolute module specifier like "dependency",
produce the module specifier in the dependency, like ".".
For a deeper path like "@org/dep/aux" and a prefix like "@org/dep", produce
"./aux".

@param {string} moduleSpecifier
@param {string} prefix
@returns {string=}