Add button icon gap prop

[AMoo-Miki]

Description

Add button icon gap prop

Check List

• New functionality includes testing.
• New functionality has been documented.
• All tests pass
  • yarn lint
  • yarn test-unit
• Update CHANGELOG.md
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[virajsanghvi]

Change looks good - I'm not sure how much I like giving this much control to consumers but hopefully people stick with defaults.

[opensearch-trigger-bot]

The backport to 1.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/oui/backport-1.x 1.x
# Navigate to the new working tree
pushd ../.worktrees/oui/backport-1.x
# Create a new branch
git switch --create backport/backport-1367-to-1.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7bdea7afd9874e3c1b5ad75e5beb62763dcc7fe7
# Push it to GitHub
git push --set-upstream origin backport/backport-1367-to-1.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/oui/backport-1.x

Then, create a pull request where the base branch is 1.x and the compare/head branch is backport/backport-1367-to-1.x.