RFC: Local snapshot file format (#25)

* adds local snapshot file format RFC

* removes hackmd heading

* adds more open questions

* fixes GH omitting array types

* also fix omitted type for output array

* removes redundant </b> tag

* adds version byte

* use new format

* removes hackmd fields

* use uint16 for utxo index

* adds missing header

* updates local snapshot RFC

* Update text/0000-local-snapshot-file-format/0000-local-snapshot-file-format.md

Co-authored-by: Thibault Martinez <thibault.martinez.30@gmail.com>

* Update text/0000-local-snapshot-file-format/0000-local-snapshot-file-format.md

Co-authored-by: Thibault Martinez <thibault.martinez.30@gmail.com>

* Update text/0000-local-snapshot-file-format/0000-local-snapshot-file-format.md

Co-authored-by: Thibault Martinez <thibault.martinez.30@gmail.com>

* Update text/0000-local-snapshot-file-format/0000-local-snapshot-file-format.md

Co-authored-by: Thibault Martinez <thibault.martinez.30@gmail.com>

* Update text/0000-local-snapshot-file-format/0000-local-snapshot-file-format.md

Co-authored-by: Thibault Martinez <thibault.martinez.30@gmail.com>

* adds network id

* removes milestone hashes

* adjusts format

* update to table notation

Co-authored-by: Thibault Martinez <thibault.martinez.30@gmail.com>