A minor release, mainly aimed at releasing a version with go.mod.

• Added go.mod
• Fixed block parsing for fenced code blocks in lists (issue #239)
• Added a link to bfchroma
• Enhanced support for info strings in fenced code blocks (issue #410)

Huge thanks to the contributors! Bjørn Erik Pedersen (@bep) Nathan Glenn (@garfieldnate) Tim Fogarty (@tfogo) Yoshiya Hinosawa (@kt3k)