README: mention pipenv in invocations

README.md

@@ -4,11 +4,11 @@
 
 1. a project to discover how much of the Web (browser APIs, JS features, HTTP headers, etc.) will work under Surfly.
 2. the data gathered from our investigations, stored under `features/`.
- - run `populate.py` to create new features and remove old features as needed
+ - run `pipenv run ./populate.py` to create new features and remove old features as needed
 3. a [nice interface](https://app.pagescms.org/surfly/compat) for devs to update Surfly compatibility data.
  - uses Pages CMS, which can be configured using `.pages.yml`
 3. a [demo page](https://surfly.github.io/compat) which injects this data into browser compatibility tables on the MDN website.
  - the source of this demo page is stored under `docs/`[^1] and hosted by Github pages
- - run `overlay.py` to create JSON files of browser compatibility data in the format used by MDN; generated data will be saved in the `data` branch of this repository
+ - run `pipenv run ./overlay.py` to create JSON files of browser compatibility data in the format used by MDN; generated data will be saved in the `data` branch of this repository
 
 [^1]: The demo page source is stored in a directory named `docs` because this is the only non-root directory name that gh-pages can deploy from without creating a custom Github Actions workflow.