Improve "On this day" feature

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If the marker text includes date ranges, the "On this day" feature may only recognize either the start or the end of the range depending on how the range is worded. Need to decide a more consistent way of parsing such date ranges and whether dates in between the range should be included (maybe depending on how long the date range is).

Examples of short date ranges:

• Q53087133: Simbahan ng Pateros — "1–2 Enero 1897" (2 days)
• Q63350694: Pag-aaklas ng Rehimyento ng Tayabas — "1–4 Nobyembre 1841" (4 days) and "20–21 Enero 1843" (2 days)

Examples of long date ranges:

• Q56070586: Diego de la Viña (1849–1920) — "25 Nobyembre – 15 Mayo 1899"
• Q76823127: Hukbong Gerilya ng mga Tsino-Filipino Laban sa mga Hapon sa Pilipinas Wha Chi — "9 Mayo – 3 Hunyo 1943"
• Q65953961: Liberation of Manila (February 3 – March 3, 1945)