VSCode: add a developer dependency on esbuild

This will allow us to follow best practices as suggested by VSCode and
package the JavaScript dependencies for the SourceKit-LSP plugin.

Author: compnerd

Editors/vscode/package-lock.json

@@ -32,6 +32,7 @@
     "devDependencies": {
         "@types/node": "^14.14.13",
         "@types/vscode": "^1.52.0",
+        "esbuild": "^0.12.9",
         "typescript": "^4.1.3",
         "vsce": "^1.81.1"
     },