GSOC2025: Json Library for D, weekly update #8

[Gaofei]

Since we've already established a framework for customized 
deserialization and added some tests (such as case 
insensitivity), we now want to incorporate case insensitivity as 
an optional feature into the default deserialization policy.
https://github.com/schveiguy/jsoniopipe/pull/54
https://github.com/schveiguy/jsoniopipe/pull/57

The insensitivity in the test is like:
```d
static struct CaseInsensitivePolicy {

         void onField(JT, T, C)(ref JT tokenizer, ref T item, 
JSONItem key, ref C context) {
             // Case-insensitive comparison
             import std.string : icmp;
             alias members = SerializableMembers!T;

             auto keyStr = key.data(tokenizer.chain);

             static foreach(i, memberName; members) {
                 {
                     enum jsonName = memberName;
                     if (icmp(keyStr, jsonName) == 0) {
                         deserializeImpl(this, tokenizer, 
__traits(getMember, item, memberName));
                         context[i] = true;
                         return;
                     }
                 }
             }
             throw new JSONIopipeException(format("No member named 
'%s' in type `%s`", keyStr, T.stringof));
         }
     }
```