A serde helper function for deserializing file size input flexibly and robustly.
Accepts either:
1) a "human" size string, e.g. "1k", "5mb", "12GiB", etc. 2) an integer number of bytes
```rust use serde::Deserialize; use deserializefilesize::deserializefilesize;
struct FileSize { #[serde(deserializewith = "deserializefile_size")] sz: usize, }
let sizestr = r#"{"sz": "42mb"}"#;
asserteq!(
serdejson::fromstr::
let intbytes = r#"{"sz": 4096}"#;
asserteq!(
serdejson::fromstr::