add save/load

[ldemailly]

serialize deser the state(s) - with some versioning

[ldemailly]

probably use https://github.com/klauspost/compress/tree/master/zstd#zstd
eventually with a dictionary

consider whether to normalize, maybe that does a grol format

ps: right now some output of printing the ast doesn't actually produce code that can be reprised to identity

will file a new ticket about that part

[ldemailly]

grol -format is done

also now (#84) there is a compact version - though without comments

probably can use token+len of literal+literal -or- use space or something url save as separator

[ldemailly]

Added a "share" button as part of #86 for the wasm/online version