Csiread

- update examples
- new feature: add `__getitem__`
- new feature: add `get_scaled_csi_sm(), apply_sm()`

- fix bug: choose big endian or little endian when using Atheros, e.g. csidata.read(endian='big')

- fix bug: some value error on 32-bit computer
- fix bug: avoid built-in keyword, len -> lens
- new example: add `example/csishow.py` to plot data
- new example: add `example/csisplit.py` to split the data file of linux-80211n-tool into small pieces

- fix bug: report format error
- fix bug: `count` value error
- new feature: add support for Atheros
- new feature: add processing functions of Intel5300: `get_scaled_csi(), get_total_rss()`
- new example

- fix bug(21): `nrxnum` and `ntxnum` should not be checked if `csi_len == 0`.
- fix bug(31): it can be built with Cython>=3.0
- fix bug(36): `NexmonPull46.rssi` should be parsed as `int8`.
- fix bug(38): `buf_noise_mem` is not initialized in `get_scaled_csi()` method.
- fix bug: k_1 should be k[0] in `utils.calib`.
- compatibility: works with numpy2.0 (37).
- update examples: upgrade dependencies of some examples
- fix some typos.