Implement ElementType.kCharStar

[nsmith-]

This type is used in the StreamerInfo for the TString class, which suggests its implementation.
Here I'm printing out the TString streamer from uproot-sample-5.25.02-uncompressed.root:

TStreamerInfo(
    fVersion=1,
    fUniqueID=0,
    fBits=50331648,
    pidf=None,
    fName=TString(fString=b"TString"),
    fTitle=TString(fString=b""),
    fCheckSum=1332649469,
    fClassVersion=1,
    fObjects=TObjArray(
        fVersion=1,
        fUniqueID=0,
        fBits=50331648,
        pidf=None,
        fName=TString(fString=b""),
        fSize=1,
        fLowerBound=0,
        objects=(
            TStreamerBasicType(
                fVersion=1,
                fUniqueID=0,
                fBits=50331648,
                pidf=None,
                fName=TString(fString=b"fData"),
                fTitle=TString(fString=b"ref. counted data (TStringRef is in front)"),
                fType=ElementType.kCharStar,
                fSize=8,
                fArrayLength=0,
                fArrayDim=0,
                fMaxIndex=ArrayDim(dim0=0, dim1=0, dim2=0, dim3=0, dim4=0),
                fTypeName=TString(fString=b"char*"),
            ),
        ),
    ),
)


@serializable
class TString(StreamedObject):
    fData: Annotated[bytes, Fmt("charstar")]