[Feature]: Custom styling option for Sonner

[jpdevdotcom]

Describe the feature

Create an additional option for custom styling so that the sonner/toast won't just stick to the white and dark theme.

Additional information

• I intend to submit a PR for this feature.
• I have already implemented and/or tested this feature.

[sadeghbarati]

Hi, check these related issues

• Override default transition styles xiaoluoboding/vue-sonner#147 (comment)
• [Bug]: Sonner Toast can only be white and plain; no styling like toast #1405