fix: fill types

[k10wl]

Fix for mismatch types for fill types

Please check if the PR fulfills these requirements

• It's submitted to right branch according to our branching model
• It's right issue type on title
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)
• It does not introduce a breaking change or has description for the breaking change

Description

Documentations states that objects can have fill option as either string or ShapeFillOption, but it was not typed.
rel: https://nhn.github.io/tui.image-editor/latest/ShapeFillOption

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[stale]

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