Remove npm msgpack dependency

[Shougo]

No description provided.

[Shougo]

error: TS2352 [ERROR]: Conversion of type 'string | number | bigint | boolean | Uint8Array | readonly ValueType[] | ValueMap | null' to type 'Jisyo' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  Type 'ValueMap' is missing the following properties from type 'Jisyo': okuri_ari, okuri_nasi
    const jisyo = msgpackDecode(data) as Jisyo;
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at file:///home/runner/work/skkeleton/skkeleton/repo/denops/skkeleton/sources/deno_kv.ts:241:19

TS2352 [ERROR]: Conversion of type 'string | number | bigint | boolean | Uint8Array | readonly ValueType[] | ValueMap | null' to type 'Jisyo' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  Type 'ValueMap' is missing the following properties from type 'Jisyo': okuri_ari, okuri_nasi
    const jisyo = msgpackDecode(data) as Jisyo;
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at file:///home/runner/work/skkeleton/skkeleton/repo/denops/skkeleton/sources/skk_dictionary.ts:161:19

Found 2 errors.

Hm...

[kuuote]

Thanks.