Documentation improvements

[matsvanes]

Please keep track of documentation problems (especially tutorials) here.

[cgohil8]

The static AEC tutorial (https://osl-dynamics.readthedocs.io/en/latest/tutorials_build/static_aec_analysis.html) calculates AEC using:

methods = {
    "filter": {"low_freq": 7, "high_freq": 13},
    "amplitude_envelope": {},
    "standardize": {},
}

I think maybe it should be:

methods = {
    "standardize": {},
    "filter": {"low_freq": 7, "high_freq": 13},
    "amplitude_envelope": {},
}

I.e. the raw data is standardised but the amplitude envelopes are left are they are. I'm not completely sure what the most standard/common approach is.

Note, the amplitude envelopes are used to calculate functional connectivity (correlation) matrices after this.