Provide helpers to handle a dataframe?

[severo]

See https://github.com/hyparam/hightable/blob/master/src/helpers/dataframe/types.ts

We would have to:

• handle the cache (maybe with LRU eviction)
• logic to estimate where (byte range) to look for a given row
• allow passing a function fn(row) => rowNumber (rowNumber = row number, sorted from 0 to N-1) and use it with a bisection algorithm to fetch the expected row, by trying to fetch ranges until narrowing to the expected row.