Add composer.json

[mlutfy]

Makes it easier to handle code updates when using composer.

[twomice]

@mlutfy I like the idea here. Quick question: is there a common standard naming convention for properties like name and type on civicrm extensions? (Revealing my composer ignorance here.)

[mlutfy]

@twomice The convention is:

• name civicrm/short-name
• description: similar to what's in the info.xml

I defer to the folks of iXiam, who have been encouraging this convention: https://lab.civicrm.org/extensions/summernote/-/blob/1.x/composer.json

civix discussions: totten/civix#267

[twomice]

Merged -- thanks @mlutfy !