prepare 2.1.1 release (#86)

## [2.1.1] - 2023-08-02
### Fixed:
- Fixed `ldclient_instance:options()` to include new `redis_tls` option.
Only specs affected.

---------

Co-authored-by: zurab-darkly <56062336+zurab-darkly@users.noreply.github.com>
Co-authored-by: Ben Woskow <48036130+bwoskow-ld@users.noreply.github.com>
Co-authored-by: Joe Cieslik <5600929+torchhound@users.noreply.github.com>
Co-authored-by: Zurab Davitiani <zurab@launchdarkly.com>
Co-authored-by: LaunchDarklyCI <dev@launchdarkly.com>
Co-authored-by: elliot <elliot@debian.elliot>
Co-authored-by: elliot <https://Apache-HB@github.com>
Co-authored-by: Elliot <35050275+Apache-HB@users.noreply.github.com>
Co-authored-by: Ben Woskow <bwoskow@launchdarkly.com>
Co-authored-by: LaunchDarklyReleaseBot <launchdarklyreleasebot@launchdarkly.com>
Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>
Co-authored-by: Matt Glover <mpglover@gmail.com>
Co-authored-by: Molly <molly.jones@launchdarkly.com>
Co-authored-by: Ben Levy <benjaminlevy007@gmail.com>
Co-authored-by: Casey Waldren <cwaldren@launchdarkly.com>
Co-authored-by: Louis Chan <lchan@launchdarkly.com>
Co-authored-by: Ember Stevens <ember.stevens@launchdarkly.com>
Co-authored-by: Ember Stevens <79482775+ember-stevens@users.noreply.github.com>
Co-authored-by: ld-repository-standards[bot] <113625520+ld-repository-standards[bot]@users.noreply.github.com>
Co-authored-by: Kane Parkinson <93555788+kparkinson-ld@users.noreply.github.com>

Author: 18 people

src/ldclient_instance.erl

@@ -31,6 +31,7 @@
     redis_database => integer(),
     redis_password => string(),
     redis_prefix => string(),
+    redis_tls => [ssl:tls_option()] | undefined,
     use_ldd => boolean(),
     cache_ttl => integer(),
     send_events => boolean(),

test-usage/ldclient_usage.erl

@@ -34,6 +34,9 @@ init_with_all_options() ->
         redis_database => 0,
         redis_password => "password",
         redis_prefix => "prefix",
+        redis_tls => [
+            {verify, verify_peer}
+        ],
         use_ldd => false,
         cache_ttl => 1000,
         send_events => false,