Fix textarea padding

[mauromascarenhas]

Proposed changes

Fix textarea padding which is currently not being inherited from "default input styles".

The textarea content is being currently overlaped by its label when not active and zero-padded in every context (focused/not focused).

Summary:

• Fixed stylesheet rules (padding in materialize-texarea class);
• Added new sample for textarea with custom placeholder;
• Added placeholder for textarea samples (enable floating label).

Screenshots (if appropriate) or codepen:

Current behaviour

Focused:

Not focused:

New behaviour

Focused:

Not focused:

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to change).

Checklist:

• I have read the CONTRIBUTING document.
• My commit messages follows the conventional commit format
• My change requires a change to the documentation, and updated it accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[wuda-io]

LGTM