Add samples as init template

[infotexture]

Description

This pull request adds the DITA garage samples and Ant build scripts from docsrc/samples/ as a new samples template:

• The files added here are the latest versions from the 4.3 release branch in the docs repo:
  https://github.com/dita-ot/docs/tree/release/4.3/samples.
• The garage samples on the release branch have not been modified since the 4.2.4 release:
  https://github.com/dita-ot/docs/tree/4.2.4/samples.

Motivation and Context

• This pull request serves as an illustration of how users could contribute a new set of template files to the init plug-in.

  A link to this PR could be referenced in the docs.

• If this PR is merged, we could remove the garage samples from docsrc/samples folder of the distribution package.

  We could then explain in the documentation how to use the init plug-in to restore them if necessary.
  This example would show how the init plug-in works.

How Has This Been Tested?

• Made a .zip file of my local copy of the init plug-in, and installed it
• Temporarily removed the garage samples from my docs clone
• Ran dita init samples -o /path/to/docs/samples
  ✅ Sample files re-appeared as expected
• Verified that the restored files are identical to those that were removed
  ✅ Git worktree clean

Type of Changes

• New feature (non-breaking change which adds functionality)

Documentation and Compatibility

• What documentation changes are needed for this feature?
  • Add info to Migration section and 4.3 Release Notes to describe the changes.
• Will this change affect backwards compatibility or other users' overrides?
  • Since this plug-in itself is new, there are no issues with backwards compatibility
  • If the samples are removed from the docs, any user scripts that rely on them would fail, but we can provide instructions for restoring them, so this shouldn't be a problem.