New writeup for intent examples

Hello all,

Regrets for tomorrow's meeting, I will be having cataract surgery.

https://mathml-refresh.github.io/mathml/docs/intent.html

On the plus side, I did my homework, and created a new document to describe
as best I can what I believe is the latest consensus on the intent
attribute.  Not the final word, as there are still things to discuss, and
it is certainly biased toward my preferences, but hopefully not too badly.

I was able to include examples that should address Bruce's concerns with
the handling of transpose.  To be continued.

If an element has sub elements with intent, then intent="fn" will collect
them as arguments to fn.  If an element has no such sub elements, then
intent="transpose" gives the intent of the transpose function itself, with
no arguments.  If an operator has no arguments, and you want the intent of
the application of the function, use intent="fn()".  Easy as pi, but we
should discuss.

The operator name can be placed on the enclosing element for the apply, or
on an element that gives markup for the operator.  This should allow for
what folks want, but we should discuss.

I've included examples with both argument index references, and argument
name references.  I'd really like to avoid XPath references.

I was able to expand on Bruce's examples where multiple
infix/prefix/postfix operators appear in a single mrow, and I marked up
both minimal-mrow and complete-mrow versions of each example.  To be
discussed.

I've included examples with integrals of fractions where the differential
is included in the fraction.  We should discuss scoping of argument name
references.

I've not said anything about literal references, which I intend to add.

Oh yes, and I still need to convert this to markdown, once we stop adding
examples to it.  I've not gone through the entire encyclopaedia.

This version is intended to be more descriptive than prescriptive.  The
examples are informally grouped to illustrate how to use the syntax.

Enjoy,
Sam