docs: update examples to use struct-based Operation syntax

Replace quoted field names with struct field syntax in all documentation examples.
Updated README.md, docs/json-patch.md, and docs/json-predicate.md to consistently
use Op, Path, Str fields instead of "op", "path", "str" quoted keys.

Author: kaptinlin

README.md

@@ -321,19 +321,19 @@ fmt.Printf("Version: %d, Status: %s, Enabled: %t\n",
 patch := []jsonpatch.Operation{
     // Test current value before modifying
     {
-        "op":    "test",
-        "path":  "/version",
+        Op:    "test",
+        Path:  "/version",
         Value: 1,
     },
     // Make the change
     {
-        "op":    "replace",
-        "path":  "/status",
+        Op:    "replace",
+        Path:  "/status",
         Value: "updated",
     },
     // Increment version
     {
-        "op":   "inc",
+        Op:   "inc",
         Path: "/version",
         Inc:  1,
     },
@@ -360,8 +360,8 @@ var patch []jsonpatch.Operation
 // Update multiple items efficiently
 for i := 0; i < itemCount; i++ {
     patch = append(patch, jsonpatch.Operation{
-        "op":    "replace",
-        "path":  fmt.Sprintf("/items/%d/status", i),
+        Op:    "replace",
+        Path:  fmt.Sprintf("/items/%d/status", i),
         Value: "processed",
     })
 }
@@ -375,19 +375,19 @@ result, err := jsonpatch.ApplyPatch(doc, patch)
 patch := []jsonpatch.Operation{
     // Add to end of array
     {
-        "op":   "add",
+        Op:   "add",
         Path: "/users/-",
         Value: map[string]interface{}{"name": "New User"},
     },
     // Insert at specific position
     {
-        "op":   "add",
+        Op:   "add",
         Path: "/tags/0",
         Value: "important",
     },
     // Remove array element
     {
-        "op":   "remove",
+        Op:   "remove",
         Path: "/items/2",
     },
 }
@@ -401,17 +401,17 @@ result, err := jsonpatch.ApplyPatch(doc, patch)
 patch := []jsonpatch.Operation{
     // Insert text at position
     {
-        "op":   "str_ins",
+        Op:   "str_ins",
         Path: "/content",
         Pos:  0,
-        "str":  "Prefix: ",
+        Str:  "Prefix: ",
     },
     // Insert at end
     {
-        "op":   "str_ins",
+        Op:   "str_ins",
         Path: "/content",
         Pos:  20,
-        "str":  " (Updated)",
+        Str:  " (Updated)",
     },
 }
 

docs/json-patch.md

@@ -133,8 +133,8 @@ var patch []jsonpatch.Operation
 // Update multiple fields
 for i := 0; i < 3; i++ {
     patch = append(patch, jsonpatch.Operation{
-        "op":    "replace",
-        "path":  fmt.Sprintf("/items/%d/status", i),
+        Op:    "replace",
+        Path:  fmt.Sprintf("/items/%d/status", i),
         Value: "processed",
     })
 }

docs/json-predicate.md

@@ -165,7 +165,7 @@ All conditions must be true.
 
 ```go
 {
-    "op": "and",
+    Op: "and",
     Apply: [
         {Op: "defined", Path: "/user/email"},
         {Op: "type", Path: "/user/age", Value: "number"},
@@ -180,7 +180,7 @@ At least one condition must be true.
 
 ```go
 {
-    "op": "or",
+    Op: "or",
     Apply: [
         {Op: "contains", Path: "/tags", Value: "admin"},
         {Op: "contains", Path: "/tags", Value: "moderator"}
@@ -194,7 +194,7 @@ Invert a condition.
 
 ```go
 {
-    "op": "not",
+    Op: "not",
     Apply: [
         {Op: "contains", Path: "/tags", Value: "banned"}
     ]
@@ -208,7 +208,7 @@ Invert a condition.
 ```go
 patch := []jsonpatch.Operation{
     {
-        "op": "and",
+        Op: "and",
         Apply: []jsonpatch.Operation{
             {Op: "defined", Path: "/user/name"},
             {Op: "defined", Path: "/user/email"},
@@ -225,11 +225,11 @@ patch := []jsonpatch.Operation{
 ```go
 patch := []jsonpatch.Operation{
     {
-        "op": "or",
+        Op: "or",
         Apply: []jsonpatch.Operation{
             {Op: "contains", Path: "/roles", Value: "admin"},
             {
-                "op": "and",
+                Op: "and",
                 Apply: []jsonpatch.Operation{
                     {Op: "contains", Path: "/roles", Value: "user"},
                     {Op: "contains", Path: "/permissions", Value: "write"},
@@ -247,7 +247,7 @@ patch := []jsonpatch.Operation{
     {Op: "defined", Path: "/required_field"},
     {Op: "type", Path: "/required_field", Value: "string"},
     {
-        "op": "not",
+        Op: "not",
         Apply: []jsonpatch.Operation{
             {Op: "test", Path: "/required_field", Value: ""},
         },