Is the input vector(ish)?
Examples
## TRUE ====
isVectorish(character())
#> [1] TRUE
isVectorish(factor())
#> [1] TRUE
isVectorish(integer())
#> [1] TRUE
isVectorish(logical())
#> [1] TRUE
isVectorish(S4Vectors::Rle())
#> [1] TRUE
## FALSE ====
isVectorish(data.frame())
#> [1] FALSE
isVectorish(matrix())
#> [1] FALSE
isVectorish(S4Vectors::DataFrame())
#> [1] FALSE