docs: add release template for automated release notes

Adds Mustache-style release template with conditional blocks
for build, features, and bugfixes sections.

Refs: #14

Author: piraz

.github/release_template.md

@@ -0,0 +1,22 @@
+# What's new in Candango NvimM {{VERSION}}
+
+## {{DATE-Jan-01-2026}}
+
+We are pleased to announce the release of NvimM {{VERSION}}.
+
+Here are the highlights:
+
+{{#BUILD}}
+### Build
+{{BUILD_CHANGES}}
+{{/BUILD}}
+
+{{#FEATURES}}
+## Features
+{{FEATURE_CHANGES}}
+{{/FEATURES}}
+
+{{#BUGFIXES}}
+## Bug Fixes
+{{BUGFIX_CHANGES}}
+{{/BUGFIXES}}