add a new constrained optimization lecture with two variables

[shlff]

as discussed

[jstac]

@HengchengZhang , could you please remind me to discuss this with you when I get back?

I have this all in a mix of LaTeX and Python --- it just needs to be combined into myst.

[HengchengZhang]

No worries @jstac! Will keep this in mind.

[HengchengZhang]

Hi @jstac, just a quick reminder for this issue. I am perfectly available to talk about this.

[jstac]

Thanks @HengchengZhang . Will you be in today? If so let's chat about it.

[HengchengZhang]

Thanks @jstac, I will be in uni this afternoon and we can talk about this whenever fits you the best.