Nu Shell Development Updates

# This week in Nu #38 - andrasio did some refactoring of grouping ([#1792](https://github.com/nushell/nushell/pull/1792)) - Samboy218 made empty a calculable value for directory sizes ([#1789](https://github.com/nushell/nushell/pull/1789)) - AdminXVII moved Nu to the `directories` crate ([#1782](https://github.com/nushell/nushell/pull/1782)) - Delapouite added docs for `rename` ([#1781](https://github.com/nushell/nushell/pull/1781)) and other commands ([#1778](https://github.com/nushell/nushell/pull/1778), [#1775](https://github.com/nushell/nushell/pull/1775), [#1774](https://github.com/nushell/nushell/pull/1774), [#1761](https://github.com/nushell/nushell/pull/1761)) - daschl extended the Nu library API to allow for embedding with custom commands ([#1780](https://github.com/nushell/nushell/pull/1780)) - jonathandturner updated the README ([#1779](https://github.com/nushell/nushell/pull/1779)), released 0.14 ([#1766](https://github.com/nushell/nushell/pull/1766)), added some help examples ([#1759](https://github.com/nushell/nushell/pull/1759), [#1755](https://github.com/nushell/nushell/pull/1755)), fixed bugs in it-expansion ([#1757](https://github.com/nushell/nushell/pull/1757)), simplified list view ([#1749](https://github.com/nushell/nushell/pull/1752)) - hdhoang fixed a typo in `cal` ([#1776](https://github.com/nushell/nushell/pull/1776)) - JosephTLyons fixed a typo in `config` ([#1769](https://github.com/nushell/nushell/pull/1769)), updated `cal` docs ([#1746](https://github.com/nushell/nushell/pull/1746)), added the `cal` command ([#1739](https://github.com/nushell/nushell/pull/1739)) - thegedge added examples to some commands ([#1765](https://github.com/nushell/nushell/pull/1765)) - elichai added the ability for help to have examples ([#1752](https://github.com/nushell/nushell/pull/1752)) - nespera fixed the help text for the `alias` command ([#1742](https://github.com/nushell/nushell/pull/1742)) - 1ntEgr8 fixed a bug in `start` ([#1738](https://github.com/nushell/nushell/pull/1738)) - ryepesg started a new book chapters comparing to imperative and functional langauges ([#82](https://github.com/nushell/book/pull/82)) - jzaefferer updated the book introduction to the latest Nu ([#77](https://github.com/nushell/book/pull/77)) - Also _big_ thanks to mhmdanas, 0xABAD, hilias, andrasio, Dimagog, rutrum, fdncred for fixing typos in the book

This week's Nu Shell development updates include refactoring of grouping, calculable empty directory sizes, migration to the 'directories' crate, documentation improvements for commands like 'rename', extension of the Nu library API for embedding with custom commands, README updates, bug fixes, help examples, typo fixes in 'cal' and 'config', the addition of the 'cal' command, examples added to commands, improvements to help functionality, and updates to the Nu book.