Update build_rpi instructions

[jay-m-dev]

Added aliroed-docker.service and instructions for enabling this service.
Added more instructions to build the aliro-imager.exe

[coveralls]

Pull Request Test Coverage Report for Build 6805245285

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.102%

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Totals
Change from base Build 6512047778:	0.0%
Covered Lines:	4335
Relevant Lines:	5280

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💛 - Coveralls