Nu Shell Updates: New Commands, Features, and Fixes

1st chunk of `blog/2020-12-25-twin0070.md`

fdc3e89733728b5c456ed83c8614934eb1fd094fac56816700000001000002a4

# This week in Nu #70

- jonathandturner added the [`set-env` command](https://github.com/nushell/nushell/pull/2802) for setting environment variables in scope, added the [`source` command](https://github.com/nushell/nushell/pull/2803) for running a script in the current context/scope, simplified [`if` to be standalone rather than stream-based](https://github.com/nushell/nushell/pull/2805), added [experimental support for flags in custom commands](https://github.com/nushell/nushell/pull/2808), added support for [custom subcommands](https://github.com/nushell/nushell/pull/2814)
- scrabsha fixed [broken links in the README](https://github.com/nushell/nushell/pull/2813)

Title: Nu Shell Updates: New Commands, Features, and Fixes

Summary

This week's Nu shell updates include the addition of the `set-env` and `source` commands, a simplified `if` command, experimental support for flags in custom commands and custom subcommands, and a fix for broken links in the README.