Changes since v6.1.2

monorepo:

• Use blazediff to speed up visual diffs (thanks @teimurjan!) (via feat: use blazediff to speed up visual diffs #4125)
• Update version in specs (thanks @domoritz!) (via fix: update version in specs #4045)

vega:

• Export schema from Vega package (thanks @domoritz!) (via feat: export schema from vega package #4046)

vega-loader:

• Correct mode handling in loader (thanks @domoritz!) (via fix: correct mode handling in loader #4048)

vega-util:

• Fix handling of null values in stringValue (thanks @domoritz!) (via fix: fix handling of null values in stringValue #4127)
• Replace all problematic Unicode characters (thanks @basbroek!) (via fix: replace all problematic Unicode characters #4130)

docs:

• Update links to Prefuse and Protovis (thanks @star1327p!) (via docs: Update links to Prefuse and Protovis #4095)
• Replace version in specs (thanks @domoritz!) (via docs: replace version in specs #4085)
• Update file name in weather example (thanks @domoritz!) (via fix: update file name in weather example #4083)
• Update versions in docs (thanks @domoritz!) (via docs: update versions in docs #4050)
• Update of the labelled donut example (thanks @PBI-David!) (via docs: update of the labelled donut example  #4064)
• Addition of the labelled donut example (thanks @PBI-David!) (via docs: addition of the labelled donut example #4062)