c2 chart reference issues

description of `Page` objects are missing, and the link here points to a non-existent heading:

https://github.com/Cytoid/wiki/blob/main/docs/en/reference/chart/c2-format.md?plain=1#L39


`is_forward` is missing description here:

https://github.com/Cytoid/wiki/blob/main/docs/en/reference/chart/c2-format.md?plain=1#L100


`ChartEvent` is missing details explaining the type and args.