add html support for title and description

[SatishB15]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our
  guidelines: https://github.com/tutkli/ngx-sonner/blob/main/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

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

What is the current behavior?

• The content or title passed to the notification only supports plain text.
• If the value contains HTML tags (e.g., Warning), it is rendered as raw text, not formatted.
• There is no automatic detection of HTML content.
• Developers cannot display styled or formatted messages using innerHTML.

Example (before fix):
content: '<strong>Warning:</strong> Something went wrong'

Rendered as:
<strong>Warning:</strong> Something went wrong

Closes #42

What is the new behavior?

• The notification system now detects when the content includes HTML.
• If HTML is present, it is safely rendered inside a <span [innerHTML]="..."> wrapper.
• If the content is plain text, it continues to display normally with no changes.
• This allows developers to send formatted messages directly.

Example (after fix):
content: '<strong>Warning:</strong> Something went wrong'

Rendered as:
Warning: Something went wrong

Does this PR introduce a breaking change?

• Yes
• No

Other information