Update yargs to version 4.6.0 🚀

[greenkeeperio-bot]

Hello :wave:

:rocket::rocket::rocket:

yargs just published its new version 4.6.0, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of yargs – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

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The new version differs by 526 commits .

• 5bcb928 docs(environment): document nested options in environment variables (#476)
• 26bad52 chore(release): 4.6.0
• f70f801 feat: switch to standard-version for release management
• f915dd4 feat: upgrade to version of yargs-parser that introduces some slick new features, great work @elas7. update cliui, replace win-spawn, replace badge. (#475)
• 3ade674 docs(license): update license to reflect work undertaken since project was forked from optimist
• c46d7e1 fix(my brand!): I agree with @osher lightweight isn't a huge selling point of ours any longer, see #468
• c48dcd9 docs: fix link in docs, add link to our new standard-changelog format (#473)
• a977ed7 see changelog for details
• 86416c8 feat(completion): completion now better handles aliases, and avoids duplicating keys.
• eb6e03f fix(windows): handle $0 better on Windows platforms
• a2b5a2a feat(conventional-changelog): switching to using conventional-changelog for generating the changelog
• 51d926e feat(commands): implemented variadic positional arguments
• 066972b docs(cleanup): Add missing features to README docs
• 0413dd1 feat(config): If invoking .config() without parameters, set a default option
• e6f957b see changelog

There are 250 commits in total. See the full diff.

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