Add more normalization methods

[maurov]

@newville as a follow-up of the Q2XAFS presentation on tender X-ray data, I think it would be great to add more (simple) normalization methods to Larch. Here a first list of what I have in mind. Feel free to comment here or we will discuss in a next developers' meeting.

• no normalization: in case one wants to work with a dataset that does not need normalization or has been normalized elsewhere
• area: simple normalization by area (nicely explained for HERFD-XANES in a recent paper https://doi.org/10.1107/S1600577524005307)
• min-max: simple normalization by min-max difference