feat(RollingText): add `RollingTextGroup`

[nemo-shen]

issue: #12477

Consider rolling-text-group is a new component, we should upgrade the minor version v4.8.x -> v4.9.0.

rolling-text-group's main goal is to control multiple rolling-text in order to support more scenes for dev. It doest change old using of rolling-text.

Demo

<RollingTextGroup>
  <VanRollingText :target-num="6" />
  <VanRollingText :target-num="6" />
  <span style="display: inline;">.</span>
  <VanRollingText :target-num="6" />
  <VanRollingText :target-num="6" />
</RollingTextGroup>

Main Jobs

• [x] add rolling-text-group component
• [x] add rolling-text-group test cases
• [x] update README of rolling-text, add rolling-text-group using demo

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (41bbe5b) 89.80% compared to head (d4c2fc7) 89.93%.

Files	Patch %	Lines
...s/vant/src/rolling-text-group/RollingTextGroup.tsx	93.33%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12572      +/-   ##
==========================================
+ Coverage   89.80%   89.93%   +0.12%     
==========================================
  Files         257      259       +2     
  Lines        6830     6864      +34     
  Branches     1657     1663       +6     
==========================================
+ Hits         6134     6173      +39     
+ Misses        373      368       -5     
  Partials      323      323              

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