Add Ruby/Rack application example with hot reload

[dsalahutdinov]

Description

Adds sample Ruby/Rack application with hot reload demonstration

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[dsalahutdinov]

@googlebot I signed it!

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CLAs look good, thanks!

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[codecov]

Codecov Report

Merging #3515 into master will not change coverage.
The diff coverage is n/a.

[dgageot]

Can we do something like:

• Copy Gemfile*
• Download the dependencies
• Copy the rest of the sources

[dsalahutdinov]

Hey, @dgageot , thanks for review!
It's done.

[dgageot]

This looks good, with a few more nits.
Also, can you copy the whole integration/examples/ruby to examples/ruby.

[dgageot]

nit: ADD Gemfile* ./

[dgageot]

nit: ADD . ./

[dgageot]

Have you tried?

sync:
  infer:
  - *.rb

It would be nice to demonstrate inferred sync

[dsalahutdinov]

Yep, I've changed to rack unreloader config and skaffold's option to infer. Works well

[dsalahutdinov]

It's done!