Create hello-world example

[macklinu]

This is a start at #50. The main goal of this PR is to figure out the primary structure for an example directory (README.md structure, how to install @zeit/ncc, how to communicate which commands to run, etc.) so that it becomes easier to add other examples moving forward. Feedback welcome (inline comments incoming)!

[macklinu]

🌺

[codecov-io]

Codecov Report

Merging #153 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #153   +/-   ##
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  Coverage    72.3%   72.3%           
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  Files          10      10           
  Lines         473     473           
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  Hits          342     342           
  Misses        131     131

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[macklinu]

@rauchg addressed your comments. Here are examples of running the npm scripts from the examples/hello-world directory:

[rauchg]

Thanks @macklinu

[macklinu]

@rauchg this should be a good for another review - apologies for not sending a comment after my latest commit to communicate that more clearly. Let me know if I can help out without anything else on this PR. Will keep contributing example PRs if we like the start of this format. 👍

(This PR is also good to be squashed and merged unless you'd like me to squash/rebase it manually.)

[rauchg]

Awesome @macklinu ! Next step would be to show off an example of using arg and a CLI with subcommands, where each subcommand is a different bundle