LamineCisse/BEP032-examples: channel_type added in channel.tsv (BEP standard) add PowerLineFrequency in ephys-json for ephys_nwb_petersen file add PowerLineFrequency and PowerLineFrequencyUnit in ephys-json for ephys_nix file @ StandardBepFormat

Lamine Cisse c332158044 add column PowerLineFrequency		2 lat temu
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sub-MS22_ses-PeterMS22180720110055concat_channels.tsv	d9d7dad848 gin commit from samuel-pc	2 lat temu
sub-MS22_ses-PeterMS22180720110055concat_contacts.tsv	7341a55b83 gin commit from Saksham	3 lat temu
sub-MS22_ses-PeterMS22180720110055concat_ephys.json	c332158044 add column PowerLineFrequency	2 lat temu
sub-MS22_ses-PeterMS22180720110055concat_ephys.nwb	10dfa9cc70 gin commit from nit-ope-de04	2 lat temu
sub-MS22_ses-PeterMS22180720110055concat_probes.tsv	d9d7dad848 gin commit from samuel-pc	2 lat temu