replaced with artifact 90493bcb588f7a7b0c05406d33c17e1812fe92097d34e6…

…c9349aabaa52ad89ea of https://pikchr.org/home/artifact/90493bcb588f7a7b to benefit from better usage of HEADING.

Doc typo fix reported in [/forumpost/4e01fef7d9].

FossilOrigin-Name: dc29638e0f5bd9f6ee656a3e0b4f3d9d16f97aea90ef21bfa4e046ffd7e4d3df

Provide keywords "rarr", "larr" and "leftrightarrow" as alternative

spellings for tokens "->", "<-", and "<->" (the names are based on HTML
entity names) to make it easier to embed Pikchr source text within a larger
HTML document without running into quoting issues with the "<" and ">"
characters.

FossilOrigin-Name: 1e359f8ed5392948044c69302fa4af0a69e00b7895a7f7db5d5f9ec4fcbac5c9