Allow serde types to be Decode/Encoded

[VictorKoenders]

Adds an attribute that users can add to struct fields

#[derive(bincode::Encode, bincode::Decode)]
struct Foo {
    #[bincode(with_serde)]
    serde: SerdeType
}

Also adds a struct that will wrap any serde type and implements Decode and Encode on it

Closes #433

[codecov-commenter]

Codecov Report

Merging #434 (b676dc5) into trunk (a2e7e0e) will decrease coverage by 1.41%.
The diff coverage is 9.44%.

@@            Coverage Diff             @@
##            trunk     #434      +/-   ##
==========================================
- Coverage   62.97%   61.56%   -1.42%     
==========================================
  Files          46       46              
  Lines        3236     3317      +81     
==========================================
+ Hits         2038     2042       +4     
- Misses       1198     1275      +77     

Impacted Files	Coverage Δ
derive/src/derive_enum.rs	0.00% <0.00%> (ø)
derive/src/derive_struct.rs	0.00% <0.00%> (ø)
derive/src/lib.rs	5.33% <0.00%> (ø)
derive/src/parse/mod.rs	90.74% <ø> (ø)
src/features/serde/de_borrowed.rs	0.00% <ø> (ø)
src/features/serde/de_owned.rs	0.00% <ø> (ø)
src/features/serde/mod.rs	0.00% <0.00%> (ø)
src/features/serde/ser.rs	0.00% <ø> (ø)
src/lib.rs	100.00% <ø> (ø)
derive/src/parse/body.rs	64.63% <11.11%> (-3.61%)	⬇️
... and 1 more

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