feat: show series labels API

[jung-han]

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

chart.hideSeriesLabel();
chart.showSeriesLabel();

• only for
• area
• bar
• bullet
• column
• column-line
• heatmap
• line-area
• line
• pie
• nestedPie
• treemap

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Thank you for your contribution to TOAST UI product. 🎉 😘 ✨

[lja1018]

[12/04] 리뷰완료
고생하셨습니다!

[jungeun-cho]

[12/04] 이견없습니다.:)