Configure JeffGeerling.com codebase using Mutagen for faster speed in Docker Edge build

[geerlingguy]

See: https://github.com/docker/for-mac/issues/1592

Current results:

Technique	Docker Version	composer install	Drupal install	Drupal page load
Native on macOS	N/A	1:06.55	N/A	N/A
NFS volume	Docker Desktop for Mac 2.3.0.2 (45183)	2:30.17	0:36.09	0:03.26
:rw,delegated	Docker Desktop for Mac 2.3.0.2 (45183)	2:51.90	1:19.22	0:03.11
:rw,delegated	Edge build, 'Cached' in UI	3:01.66	1:25.80	0:03.23
(May 27 attempt)	Edge build, 'Cached' in UI	1:03.15	0:30.92	0:00.83

So this is practically native performance, at the expense of a ~60 second initial sync. Very fast, very nice.

[geerlingguy]

Fixed.