fix: render slack emoji shortcodes as unicode characters (#12928)

This PR fixes an issue where Slack emojis are rendered as text
shortcodes (e.g. 🚀) instead of the actual emoji characters in
Chatwoot messages.

It introduces a new EmojiFormatter class that uses the emoji-data
mapping to convert shortcodes to unicode characters.

---------

Co-authored-by: Sony Mathew <sony@chatwoot.com>
Co-authored-by: Sony Mathew <2040199+sony-mathew@users.noreply.github.com>

spec/lib/integrations/slack/emoji_formatter_spec.rb

@@ -0,0 +1,20 @@
+require 'rails_helper'
+
+describe Integrations::Slack::EmojiFormatter do
+  describe '.format' do
+    it 'replaces emoji shortcodes with unicode characters' do
+      expect(described_class.format('Hello :smile:')).to eq('Hello 😄')
+      expect(described_class.format('Good job :+1:')).to eq('Good job 👍')
+      expect(described_class.format('Unknown :unknown_emoji:')).to eq('Unknown :unknown_emoji:')
+    end
+
+    it 'handles nil or empty text' do
+      expect(described_class.format(nil)).to be_nil
+      expect(described_class.format('')).to eq('')
+    end
+
+    it 'replaces multiple emojis' do
+      expect(described_class.format(':smile: :+1:')).to eq('😄 👍')
+    end
+  end
+end