Fix addons path alias in tsconfig (#17179)

There is a misconfiguration in the addons package tsconfig.build.json
that sets the path alias "addons" to the addons dist, while at the same
time the include section lists the addons src, and the "addons" alias is
referenced in the root index.ts for the public umd package. This results
in TypeScript seeing two different js files (modules) with the same name
and structure, but since they are different modules, they are different
types from the standpoint of TypeScript, which are not compatible in
non-duck-typing scenarios. I'm not sure how we haven't hit this in the
past, but we are hitting it now with newer PRs.

The fix is just to update the "addons" alias to point to src, which is
exactly how it is configured for other packages. I suspect this was just
a typo since addons was first introduced but somehow we just weren't
hitting errors caused by it. cc @RolandCsibrei

Author: ryantrem

packages/public/umd/babylonjs-addons/tsconfig.build.json

@@ -9,7 +9,7 @@
         "importHelpers": true,
         "paths": {
             "core/*": ["dev/core/dist/*"],
-            "addons/*": ["dev/addons/dist/*"]
+            "addons/*": ["dev/addons/src/*"]
         }
     },
     "include": ["./src/**/*", "../../../dev/addons/src/**/*"]