xcopy - assume destination is a directory

[j-piccolo]

By default xcopy asks if the destination is a file or directory. Since we know it's a directory we can add the /i flag and prevent an extra prompt.

Description of /i

If source is a directory or contains wildcards and destination does not exist, 
xcopy assumes destination specifies a directory name and creates a new directory. 
Then, xcopy copies all specified files into the new directory.

[the-mikedavis]

This table is also in the book's installation section:

helix/book/src/install.md

Lines 69 to 70 in 44b4479

	|windows(cmd.exe) |`xcopy /e runtime %AppData%/helix/runtime` |
	|windows(powershell)|`xcopy /e runtime $Env:AppData\helix\runtime` |

. Could you update the commands there too?

[j-piccolo]

Done

[the-mikedavis]

Thanks!