shtab v1.9.3 stable

• ⚒️ misc tcsh improvements & fixes (#213)
  • support positional completion under subcommands at any depth
  • guard against out-of-range array indexing
  • handle arguments with a custom .complete in the multi-requirement branch
  • complete --opt=<TAB> for options taking a value (nargs != 0)
  • deduplicate rules
• 🎣 fix fish backend (#232)
  • fix option values breaking subcommands (#228)
  • fix argument values conflicting with command names (#229)
  • handle positional order (#230)
  • fix FILE missing filenames & options unintentionally completing filenames (#227)
• 🐟 fix fish descriptions (#233 <- #231)
  • expand argparse placeholders (e.g. %(prog)s)
  • subcommand help fallback if description missing
• 🛠️ misc refactoring (#238)
  • tests debug output: minor bytes/str fix
  • inline some single-use functions
• 🗜️ tests auto-caplog (#237)
• ± tests diff examples output summary (#234)
• 🌐 update docs FAQs & URLs