x/pkgsite: missing functions for unexported embedded struct

[gonutz]

The wui library documentation is missing some functions.

Take the Button: it has an embedded textContol struct which in turn embeds control which has exported function SetX. Here are the code links:

Button
textControl
control
control.SetX(x int)

Now the documentation does not list SetX under the Button type.

This is true for a number of types but not for all of them.

As a counter example, SetX is documented to be part of FloatUpDown which has one more indirection by embedding textEditControl, which then embeds textControl as above.

FloatUpDown
textEditControl

I suspect this might be a corner case with unexported embedded structs which have exported functions.

[zigo101]

dup of #6600?

BTW, Golds shows them all: https://github.com/go101/golds