[ecash-herald] Parse app txs in daily summaries

Summary: App txs are an important KPI to track. More apps (with real users), more inelastic demand.

Test Plan:
npm test, review screenshot

yesterday's summary (before this diff)

24 hr summary from rightnow, with this diff (only bottom half, which has changed):

after feedback and new type:

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D16959