5.5.1
fix(toolbox): use `typeof` keyword rather than `isFunction` util to detect if `MouseEvent` object is supported (fix unexpected replacement in https://github.com/apache/echarts/commit/53babd2b4c83e875f8df6c370b356d6b44c1919c#diff-0b91602cf047a98c67d6c4edaacbfa7399c8e0d2d4564b83ece8419d144aea84R64)
fix: remove used default zlevel
fix(toolbox): fix toolbox text can't apply the specified or inherited font style
refact: remove all register code with side effects