docs gluon-tls: add documentation about gluon-tls feature

docs/features/tls.rst

+TLS support
+===========
+
+The generic TLS implementation which is currently used by OpenWRT can be installed or added as dependency through the package ``gluon-tls``.
+This removes the need for community packages to depend on a specific TLS implementation (like mbedtls, OpenSSL or WolfSSL).
+
+This package is a placeholder for the current TLS implementation used.
+To allow for easy usage of communicating through HTTPS from the node, typical Certificate Authorities (CAs) are included through the package ``ca-bundle`` .
+
+* Starting with OpenWRT 23.05, mbedtls is the default TLS layer - this is reflected in Gluon :ref:`v2023.2 <releases-v2023.2-minor-changes>`. HTTPS is used by default to communicate with OpenWRT opkg servers.

docs/index.rst

@@ -25,6 +25,7 @@ Several Freifunk communities in Germany use Gluon as the foundation of their Fre
   features/wlan-configuration
   features/private-wlan
   features/wired-mesh
+  features/tls
   features/dns-cache
   features/monitoring
   features/multidomain

docs/releases/v2023.2.rst

@@ -288,6 +288,7 @@ Major changes
 This release is based on the newest OpenWrt 23.05 release branch.
 It ships with Linux kernel 5.15.y, wireless-backports 6.1.24 and batman-adv 2023.1.
 
+.. _releases-v2023.2-minor-changes:
 
 Minor changes
 -------------