Properly handle GitHub Action inputs that can have multiple values

[tevanoff]

The syntax we currently propose for passing multiple values to an input in the GitHub Action is as follows:

externals: |
  - '*.sass'
  - 'public/**'

But that will be parsed into a single string with multiple lines that looks like this:

"- '*.sass'\n
- 'public/**'"

That won't behave as expected when passed along to the CLI.

The correct syntax for this should be like so:

externals: |
  *.sass
  public/**

That, along with the changes in this PR to use getMultilineInput to get those values will give us an array like we need:

["*.sass", "public/**"]

That can be passed along to the CLI, which expects a string[] for these inputs.

How to test
This has been published as chromaui/action-canary@v1 and the CLI canary is below.

Try this out with no values for the inputs, a single value for externals, and multiple values with the new syntax for externals.

📦 Published PR as canary version: 11.1.2--canary.951.8351878886.0

✨ Test out this PR locally via:

npm install chromatic@11.1.2--canary.951.8351878886.0
# or 
yarn add chromatic@11.1.2--canary.951.8351878886.0

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.00% (target: -1.00%)	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (680fb90)	8439	6640	78.68%
Head commit (2593eba)	8439 (+0)	6640 (+0)	78.68% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#951)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[ghengeveld]

🚀 PR was released in v11.1.1 🚀