docs: document installation of re2

README.md

@@ -62,6 +62,10 @@ From github
 npm install github:dilame/instagram-private-api
 ```
 
+This package uses [`url-regex-safe`](https://www.npmjs.com/package/url-regex-safe) ([GitHub](https://github.com/spamscanner/url-regex-safe)) to check for links when sending direct messages.
+By default, the **safe** regex engine [`re2`](https://github.com/uhop/node-re2) is **not** installed.
+⚠ It's highly recommended for you to install `re2` by running `npm install re2`, else you _will_ be vulnerable to [CVE-2020-7661](https://nvd.nist.gov/vuln/detail/CVE-2020-7661).
+
 # Support us
 
 If you find this library useful for you, you can support it by donating any amount