Introduce `--additional-identifier` flag

Add flag to `between` command to specified an additional custom
identifier for the named-entry list processing.

Create defaults section for report flag values

Create single place to define defaults for report option command line flags
to fix inconsistency of the usage of defaults between using `dyff` as a binary
versus using the `dyff` code in a test case.

Fix broken test case

With the unified text rendering, the unchanged output is not also
colored line by line rather than coloring the line feed character as
part of one big color format. Therefore the expected test output is
looking slightly different in raw mode.

Omit empty documents in Kubernetes compare

When comparing multi document files using Kubernetes semantics, omit empty
documents in the list of documents to compare.

Introduce multiline text difference output

Fixes homeport#171

Add human friendly difference output for multiline texts similar to the one
used by the minor change output.

Extend invalid YAML check test case

Ref: homeport#209

Add new field to the invalid YAML test case sample YAML to verify that the fix
from the `neat` package does indeed fix the reported issue.

Revert "Add `system-files` plug"

This reverts commit 64a5bd8.

Remove `netgo` build tag

Remove obsolete `netgo` build tag.

Bump github.com/onsi/gomega from 1.16.0 to 1.17.0

Bumps [github.com/onsi/gomega](https://github.com/onsi/gomega) from 1.16.0 to 1.17.0.
- [Release notes](https://github.com/onsi/gomega/releases)
- [Changelog](https://github.com/onsi/gomega/blob/master/CHANGELOG.md)
- [Commits](onsi/gomega@v1.16.0...v1.17.0)

---
updated-dependencies:
- dependency-name: github.com/onsi/gomega
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Simplify GitHub Action setup for build and test

Use Go `1.17` install instead of `go get`.

Remove step names that add no value.