[vte] build: Mention release tarballs in README

[Christian Persch <chpe src gnome org>]

commit c65d8d92a6b4be97e4d4224cda10ead5e9f413f7
Author: Christian Persch <chpe src gnome org>
Date:   Sat Apr 3 12:10:20 2021 +0200

    build: Mention release tarballs in README

 README.md | 13 +++++++++++++
 1 file changed, 13 insertions(+)
---
diff --git a/README.md b/README.md
index 74792848..51e41cce 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,19 @@ Virtual TErminal
 
 VTE provides a virtual terminal widget for GTK applications.
 
+Source & Releases
+-----------------
+
+To get the source code, use
+```
+$ git clone https://gitlab.gnome.org/GNOME/vte
+```
+
+To get the source for a release version, use the corresponding git tag, or
+download a tarball at
+https://gitlab.gnome.org/GNOME/vte/-/archive/TAG/vte-TAG.tar.bz2
+replacing `TAG` with the desired tag's name (e.g. `0.64.0`).
+
 Installation
 ------------