[lldb-dap] Adding an icon to the lldb-dap package. (#137695)

This shows up in the extension UI and in the VSCode extension
marketplace.

I used the llvm/llvm-www/blob/main/img/LLVMWyvernSmall.png for the
image.

Here is what this looks like locally: 
<img width="1020" alt="Screenshot 2025-04-28 at 12 30 33 PM"
src="https://github.com/user-attachments/assets/cd615161-06db-4a37-8f8a-df65ca620a67"
/>

lldb/tools/lldb-dap/.vscodeignore

@@ -5,5 +5,6 @@
 !LICENSE.TXT
 !package.json
 !README.md
+!llvm-logo.png
 !out/**
-!syntaxes/**
+!syntaxes/**

lldb/tools/lldb-dap/package.json

@@ -14,6 +14,7 @@
   "bugs": {
     "url": "https://github.com/llvm/llvm-project/issues"
   },
+  "icon": "llvm-logo.png",
   "keywords": [
     "C",
     "C++",