feat: adding viewmedia and viewblock scroll depth

[rpapani]

• Adding viewmedia, viewblock series
• Adding Viewmedia Depth and Viewblock Depth to Conversion chicklet in oversight (please see the screenshot)
• Depth is calculated as (median / max) * 100 of the facet data, which gives the median percent of blocks/media viewed, which is kind of representative of scroll depth. For example, if the median of viewblock is 3 and max block is 10, then 50% of the users have seen 30% of scroll depth