README table is missing `*` and `mul!`

[JeffFessler]

The README interface table
https://github.com/JuliaLinearAlgebra/ToeplitzMatrices.jl#implemented-interface
is missing * and mul! and probably more like \ and ldiv!.
Maybe they "go without saying" but I'm not 100% sure they all apply to every subtype.
I could make a PR if someone can confirm that all 4 apply to all AbstractToeplitz types.

[putianyi889]

they should belong to the LinearAlgebra section which I didn't participate, so I left that section blank.

[JeffFessler]

Since + is that table probably * belongs in that same table?

[putianyi889]

no since + is straightforward while * applies proprietary algorithms for Toeplitz

[JeffFessler]

The developer knows that, but a user's perspective is that they are both methods for the type.

[putianyi889]

they are both methods for the type.

A method doesn't always belong to the category of interface. For example, Array addition and subtraction is implemented in Base via broadcasting while Matrix multiplication is implemented in LinearAlgebra.

Anyway, I agree that * and \ can go to interface since they are at the very front end, while the underlying principles need to be explained in the section of linear algebra.

The developer knows that, but a user's perspective is that

A significant task this package does is fast linear algebra operations, as pointed out at the very beginning of README. I would say they are more important than the interface, so they need a separate section to clarify. The users also need to be aware that some proprietary algorithms are applied and they are not as reliable as the default Julia routine. The issues can confirm that.

I'm not 100% sure they all apply to every subtype. I could make a PR if someone can confirm

Me too. It's the exact reason I left the section blank. @jishnub @dlfivefifty