Add Float#pack_float32 and Float#pack_float64 methods

[postmodern]

Add methods for easily packing a Float into a float32 or float64 C type. These methods should call pack with the C type and **kwargs.

• Float#pack_float32
• Float#pack_float64

The following methods should not be passed **kwargs as they are tied to little-endian or big-endian:

• Float#pack_float32_le
• Float#pack_float64_le
• Float#pack_float32_be
• Float#pack_float64_be

Alias the *_be to *_ne or *_net?

The documentation and specs can be copied from Float#pack.

[postmodern]

Did a Mastodon poll about _ne vs. _net suffix, and appears most people say to just use _be when referring to network-byte-order types. So maybe hold off on the _ne/_net aliases until someone eventually requests them?
https://infosec.exchange/@postmodern/110459088606261323