docs: -

README.md

@@ -101,7 +101,7 @@ go install -v github.com/hueristiq/xsubfind3r/cmd/xsubfind3r@latest
 
 ## Post Installation
 
-`xsubfind3r` will work right after [installation](#installation). However, **[BeVigil](https://bevigil.com)**, **[BuiltWith](https://api.builtwith.com/domain-api)**, **[Chaos](https://chaos.projectdiscovery.io/#/)**, **[Fullhunt](https://fullhunt.io/)**, **[Github](https://github.com)**, **[Intelligence X](https://intelx.io)**, **[LeakIX](https://leakix.net)** and **[Shodan](https://shodan.io/)** require API keys to work, **[URLScan](https://urlscan.io)** supports API key but not required. The API keys are stored in the `$HOME/.config/xsubfind3r/config.yaml` file - created upon first run - and uses the YAML format. Multiple API keys can be specified for each of these source from which one of them will be used.
+`xsubfind3r` will work right after [installation](#installation). However, **[BeVigil](https://bevigil.com)**, **[BuiltWith](https://api.builtwith.com/domain-api)**, **[Certspotter](https://sslmate.com/ct_search_api/)**, **[Chaos](https://chaos.projectdiscovery.io/#/)**, **[Fullhunt](https://fullhunt.io/)**, **[Github](https://github.com)**, **[Intelligence X](https://intelx.io)**, **[LeakIX](https://leakix.net)** and **[Shodan](https://shodan.io/)** require API keys to work, **[URLScan](https://urlscan.io)** supports API key but not required. The API keys are stored in the `$HOME/.config/xsubfind3r/config.yaml` file - created upon first run - and uses the YAML format. Multiple API keys can be specified for each of these source from which one of them will be used.
 
 Example `config.yaml`:
 
@@ -114,6 +114,7 @@ sources:
     - anubis
     - bevigil
     - builtwith
+    - certspotter
     - chaos
     - commoncrawl
     - crtsh