Check compose file don't use relative paths for bind mount

[ndeloof]

- What I did Reject compose file to use a relative path for bind mount https://docker.atlassian.net/browse/APP-275

- How I did it

• checked yaml tree during init
• added volumes to partial mapping used by build and check source path

- How to verify it

• use a compose file with relative path bind mount and run docker app init
• use a docker.app and edit compose file to introduce relative path bind mount, then run docker app build

- Description for the changelog Docker app do reject compose file relying on a relative volume path

- A picture of a cute animal (not mandatory)

[codecov[bot]]

Codecov Report

Merging #742 into master will increase coverage by <.01%. The diff coverage is 71.64%.

@@            Coverage Diff             @@
##           master     #742      +/-   ##
==========================================
+ Coverage   68.97%   68.98%   +<.01%     
==========================================
  Files          64       63       -1     
  Lines        3439     3440       +1     
==========================================
+ Hits         2372     2373       +1     
  Misses        749      749              
  Partials      318      318

Impacted Files	Coverage Δ
internal/commands/build/build.go	60.4% <66.66%> (ø)	:arrow_up:
internal/packager/init.go	64.64% <70.58%> (+1.37%)	:arrow_up:
internal/commands/build/compose.go	78.57% <73.33%> (-5.22%)	:arrow_down:

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