[SUBGRAPH] Add a counter property for subscribers on an Index

[vmichalik]

No description provided.

[msoni89]

@kasparkallas

Please add more detail here.

Do you want me to increase and decrease the counter based on subscribe, or unsubscribe?

Is subscriber_count okay for the name?

[msoni89]

As per the discussion, we don't need to address it because it's already available as totalSubscriptionsWithUnits

[kasparkallas]

Thank you, @msoni89

totalSubscriptionsWithUnits actually makes more sense than just totalSubscriptions. We should also display this number in the Console. I'll make a story for that and edit this comments.

Story here: superfluid-finance/superfluid-explorer#81