rename base62.ts to base62x.ts

[wadelau]

The script:src/lib/encodings/base62.ts would be better to be renamed to src/lib/encodings/base62x.ts as the original name may lead to misunderstanding as to the actual base62, i.e., 0-61.
In fact this base62.ts is to present code number with 0-63. rt?

[fenying]

Oh, u r right. I will fix this later. Thank you.

[fenying]

Fixed in v2.2.0