build: suppress 'THIS_IS_UNDEFINED' warning in Rollup config

build: suppress 'THIS_IS_UNDEFINED' warning in Rollup config This commit adds an `onwarn` handler to `rollup.config.ts` to suppress the `THIS_IS_UNDEFINED` warning. This warning is triggered by `@actions` dependencies (specifically `@actions/core`) which are CommonJS modules that use `this` at the top level (e.g., in `__awaiter` helper). Rollup rewrites `this` to `undefined` in ES module context, which is correct behavior here as the code falls back safely. Suppressing the warning cleans up the build output. Co-authored-by: hussainweb <1040271+hussainweb@users.noreply.github.com>