refactor: use angular signals, standalone component

[lekhmanrus]

Please check if the PR fulfills these requirements

• The commit messages follow these guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other. Please describe:

If it is a Bugfix, please describe the root cause and what could have been done to prevent it…

What is the current behavior? (You can link to an open issue here, add screenshots…)
Regular @Inputs used as well as OnChanges hook.

What is the new behavior?
Angular Signals with build-in validation; refactored to standalone components.

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration
path for existing applications: …

Other information (if applicable):
close #158

I would suggest using versions consistent with major Angular versions. Let's say ngx-skeleton-loader v18 for Angular v18, etc.

Please @mention @people to review this PR…
@willmendesneto