Change and add Wikidata fields mappings

[larsgw]

See also #78

---

Wikidata property	Current mapping	Expected mapping	Notes	Status
P698	ignored	PMID		v0.3.2
P932	ignored	PMCID		v0.3.2
P407	-	language	not label	v0.4.4
P364	ignored	language	not label, lower merging priority	v0.4.4
P1104	ignored	number-of-pages		v0.3.2
P136	-	genre	not label	v0.3.2
P580	accessed	???		v0.3.2
P585	accessed	???		v0.3.2
P348	-	version		v0.3.2
-	-	original-title	possible with P364 (original language of work) and labels, but difficult with current setup	v0.4.4
P98	-	editor	name	v0.3.2
P57	-	director	name	v0.3.2
P86	-	composer	name	v0.3.2
P110	-	illustrator	name	v0.3.2
P655	-	translator	name	v0.3.2
P123	-	publisher	not label	v0.3.2
P291	-	publisher-place	not label	v0.3.2
P236	-	ISSN		v0.3.2
P179	-	collection-title	via Zotero	v0.4.4

• ignored isn't an actual CSL field, it just means that the mapping omits 'Property unknown' warnings for those properties.
• 'unreleased' is implemented, but not yet released
• versions in the status column mean completed in $VERSION

---

WIP. Feel free to add more mappings.

Helpful docs:

• Wikidata Bibliographic metadata overview
• CSL JSON spec
• Pre-existing mappings:

  citation.js/src/parse/wikidata/prop.js

  Lines 49 to 75 in 9997b0d

  	const propMap = {
  	P31: 'type',
  	P50: 'author',
  	P212: 'ISBN',
  	P304: 'page',
  	P356: 'DOI',
  	P393: 'edition',
  	P433: 'issue',
  	P478: 'volume',
  	P577: 'issued',
  	P580: 'accessed',
  	P585: 'accessed',
  	P953: 'URL',
  	P957: 'ISBN',
  	P1433: 'container-title',
  	P1476: 'title',
  	P2093: 'author',
  	// ignore
  	P2860: false, // Cites
  	P921: false, // Main subject
  	P3181: false, // OpenCitations bibliographic resource ID
  	P364: false, // Original language of work
  	P698: false, // PMID
  	P932: false, // PMCID
  	P1104: false // Number of pages
  	}