Update docs links, fix broken code

[wilfredallyn]

• Updated documentation links to point to the latest version
• Fixed code in Hello World tutorial to handle balance struct instead of u64
• Running Spending Policy tutorial Step 1a now produces this error

$ bdk-cli wallet -w carol -d $CAROL_DESCRIPTOR get_new_address
[2023-02-13T11:08:03Z ERROR bdk_cli] Descriptor(Miniscript(TypeCheck("fragment «thresh(3,pk([5f769577/84'/1'/0'/0]tpubDFBt.../*),s:pk([ef28b7c5/84'/1'/0'/0]tpubDEx.../*),s:pk(tprv8Z.../84'/1'/0'/0/*),sdv:older(2))» sub-fragment 3 is not a unit (does not put exactly 1 on the stack given a satisfying input)")))

I fixed the problem by re-compiling the miniscript policy using the playground and updating the descriptors (sdv:older(2) -> snl:older(2))

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[notmandatory]

Thanks for the fixes. I agree it makes sense to update the tutorials and other general docs to latest bdk, but for the release blog posts about older versions I'd leave those as they were pointing to the corresponding bdk releases.

[wilfredallyn]

That makes sense to leave the blog posts about older versions pointing to those releases. I revised commit 1075574 to exclude those

[notmandatory]

ACK d1c9e0e