docs: link to Docker image, APT, in release notes

relnotes/v1.md

@@ -6,3 +6,10 @@ protocol compatible with Syncthing 1.
 
 More detailed information about Syncthing 2 can be found in the release
 notes at https://github.com/syncthing/syncthing/releases.
+
+This release is also available as:
+
+* APT repository: https://apt.syncthing.net/
+
+* Docker image: `docker.io/syncthing/syncthing:{{.version}}` or `ghcr.io/syncthing/syncthing:{{.version}}`
+  (`{docker,ghcr}.io/syncthing/syncthing:1` to follow just the major version)

script/relnotes.go

@@ -22,6 +22,7 @@ import (
 	"os"
 	"regexp"
 	"strings"
+	"text/template"
 )
 
 var (
@@ -59,12 +60,24 @@ func main() {
 
 // Load potential additional release notes from within the repo
 func additionalNotes(newVer string) ([]string, error) {
+	data := map[string]string{
+		"version": strings.TrimLeft(newVer, "v"),
+	}
+
 	var notes []string
 	ver, _, _ := strings.Cut(newVer, "-")
 	for {
 		file := fmt.Sprintf("relnotes/%s.md", ver)
 		if bs, err := os.ReadFile(file); err == nil {
-			notes = append(notes, strings.TrimSpace(string(bs)))
+			tpl, err := template.New("notes").Parse(string(bs))
+			if err != nil {
+				return nil, err
+			}
+			buf := new(bytes.Buffer)
+			if err := tpl.Execute(buf, data); err != nil {
+				return nil, err
+			}
+			notes = append(notes, strings.TrimSpace(buf.String()))
 		} else if !os.IsNotExist(err) {
 			return nil, err
 		}