feat: add jetton cookbook

[pixelplex]

Closes #321

[a-bahdanau]

#321

[a-bahdanau]

There is one TODO left in PR
forwardPayload: beginCell().storeBool(false).endCell().beginParse(), // TODO: this is so gas consuming, maybe there is another way? Or use generic (TBD)? Or there is better way to just left it

Maybe wait till 1.5 for generics? Or use another approach as u suggest

[novusnota]

Great! I've added some nits from my side.

With that, I summon @Gusarich for a better proof-read of the code :)

[a-bahdanau]

@novusnota resolved your comments

[novusnota]

@a-bahdanau @pixelplex Thanks for opening the PR and working through all the suggestions we threw at you :)

@Gusarich, thanks for helping me review this! Please notify if there is anything else before we merge it?

[anton-trunov]

Thanks @a-bahdanau, we have a nice starting point to further enhance the cookbook!