minor changes, slightly smaller

Low-risk release mostly fixing a json syntax error found in the README,

• uses newer, smaller resolvewithplus, see esmock size here,
• uses a shared "moduleId not found" error message,
• removes lines not covered by tests,
• fixes a README json syntax error, updates the descriptions for some test and renames the internally-used variable modulePath to moduleId,
• removes a few chars from README