feat(command): add startup message

[rustatian]

Reason for This PR

• It was not obvious when the RR started.

Description of Changes

• Add startup message with RR version and buildtime.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.] [Reviewer TODO: Verify that these criteria are met. Request changes if not]

• [x] All commits in this PR are signed (git commit -s).
• [x] The reason for this PR is clearly provided (issue no. or explanation).
• [x] The description of changes is clear and encompassing.
• [x] Any required documentation changes (code and docs) are included in this PR.
• [x] Any user-facing changes are mentioned in CHANGELOG.md.
• [x] All added/changed functionality is tested.

[codecov[bot]]

Codecov Report

Merging #135 (f9e10d7) into master (3795a7b) will decrease coverage by 0.15%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #135      +/-   ##
==========================================
- Coverage   43.89%   43.73%   -0.16%     
==========================================
  Files          12       12              
  Lines         565      567       +2     
==========================================
  Hits          248      248              
- Misses        306      308       +2     
  Partials       11       11              

Impacted Files	Coverage Δ
internal/cli/serve/command.go	6.06% <0.00%> (-0.19%)	:arrow_down:

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