CHANGELOG, README: update for (go.field).embed

Author: ydnar

CHANGELOG.md

@@ -4,10 +4,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Added
+- [#65](https://github.com/alta/protopatch/pull/56): embedded message fields. Set `(go.field).embed = true` to embed a message field in the generated Go struct. The resulting field will be a pointer to and sharing a name with the generated Go struct.
+
 ### Updated
 - github.com/envoyproxy/protoc-gen-validate v0.6.0 → v0.6.1 (reverted breaking API change)
 - golang.org/x/tools v0.1.0 → v0.1.6
 - google.golang.org/protobuf v1.26.0 → v1.27.1
+
 ## [v0.3.4] — 2021-04-23
 
 ### Updated
@@ -22,6 +26,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - golang.org/x/tools v0.0.0-20201223225330-bdbb3c917f0b → v0.1.0
 - google.golang.org/protobuf v1.25.0 → v1.26.0
 - protoc v3.14.0 → v3.15.6
+
 ## [v0.3.2] — 2021-03-12
 
 ### Fixed

README.md

@@ -90,6 +90,53 @@ message ToDo {
 }
 ```
 
+### Embedded Fields
+
+A message field can be embedded in the generated [Go struct](https://golang.org/ref/spec#Struct_types) with the `(go.field).embed` option. This only works for message fields, and will not work for oneof fields or basic types.
+
+```proto
+import "patch/go.proto";
+
+message A {
+	B b = 1 [(go.field).embed = true];
+}
+
+message B {
+	string value = 1;
+}
+```
+
+The resulting Go struct will partially have the form:
+
+```go
+type A struct {
+	*B
+}
+
+type B struct {
+	Value string
+}
+
+var a A
+a.Value = "value" // This works because B is embedded in A
+```
+
+#### Alternate Syntax
+
+Multiple options can be grouped together with a message bounded by `{}`:
+
+```proto
+import "patch/go.proto";
+
+message A {
+	B b = 1 [(go.field) = {embed: true}];
+}
+
+message B {
+	string value = 1;
+}
+```
+
 ### Linting
 
 Protopatch can automatically “lint” generated names into something resembling [idiomatic Go style](https://golang.org/doc/effective_go.html#names). This feature should be considered *unstable*, and the names it generates are subject to change as this feature evolves.