export @using and add docstring

[hhaensel]

Loading of modules is currently done via Revise.includet()
This is slow as it doesn't allow for precompilation.

My proposal is to replace this procedure by using statements when possible.

To make that procedure easier I have written a handy @using macro that does the following.

Here's the doc string:

@using(package_path)

macro to simplify loading of modules that are not located in the LOAD_PATH

package_path can be

• a path to a directory containing a module file of the same name
  e.g 'models/MyApp' to load 'models/MyApp/MyApp.jl'
• a path to a module (without extension '.jl')
  e.g. 'models/MyApp' to load models/MyApp.jl'
• a path to a package directory containing a 'src' directory and module file therein
  e.g. 'models/MyApp' to load 'models/MyApp/src/MyApp.jl'

Examples

@using models/MyApp

@using StippleDemos/Vue3/Calendars

or explicitly

@using StippleDemos/Vue3/Calendars/Calendars

Note, directories containing special characters like colon (':') or space (' ')
need to be escaped by double quotes.

@using "C:/Program Files/Julia/models/Calendars"

# or
@using "C:/Program Files"/Julia/models/Calendars

Caveat: Due to precompilation it is not possible to supply variables to the macro.
Calls need to supply explicit paths.

[essenciary]

Pretty cool, thanks @hhaensel !

[PingoLee]

Who using @using in MVC app?