chore(deps): update @vuepress/plugin-back-to-top requirement from ^1.5.4 to ^1.9.9

[dependabot[bot]]

Updates the requirements on @vuepress/plugin-back-to-top to permit the latest version.

Changelog

Sourced from @​vuepress/plugin-back-to-top's changelog.

1.9.9 (2023-02-25)

Bug Fixes

• remove non-existing :blur css pseudo selector (#3118) (5e3a5a0) @​Niko Strijbol
• theme-default: headings anchor should not be selectable (#3063) (e5915a8) @​Rami Yushuvaev
• types: missing types for initialOpenGroupIndex (close: #3129) (#3130) (9049d48) @​ulivz
• types: missing types for nested sidebar group (close: #3127) (#3128) (74d5eec) @​ulivz

1.9.8 (2023-01-06)

Bug Fixes

• cli: .vuepress/config.ts does not respect custom command (close: #3113) (#3114) (7cd8b30) @​ulivz

1.9.7 (2022-01-18)

Bug Fixes

• types: missing ariaLabel at default theme config (a7b12bf) @​ulivz

1.9.6 (2022-01-17)

Bug Fixes

• core: compatibility with node 10 (close: #2981) (#2992) (f59598a) @​ulivz
• types: missing sidebarDepth at default theme config (5c6a16c) @​ulivz

Features

• add build concurrency control (close: #1819) (#2953) (2f9a394) @​Troy Eagle
• theme-default: set home footer with markdown slot (close: #2993) (#2994) (753df05) @​ulivz

1.9.5 (2021-12-25)

Features

... (truncated)

Commits

• f1cbdb6 build: release version 1.9.9
• 1dee30f chore(all): 1.9.8 changelog
• cb87096 build: release version 1.9.8
• 2f2357a build: release version 1.9.7
• 5699216 build: release version 1.9.6
• ef6f87a build: release version 1.9.5
• e4a28db build: release version 1.9.4
• accfe87 build: release version 1.9.3
• ed3cce6 build: release version 1.9.2
• b814133 refactor: typed all official plugins
• Additional commits viewable in compare view

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