Added YAML Rule Example (#635)

* Create find-key-value.md

* Create index.md

* fix: update playground link

* Update find-key-value.md

---------

Co-authored-by: Herrington Darkholme <[email protected]>

Author: rohitcoder

website/catalog/yaml/find-key-value.md

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+## Find key/value and show message using those key/vals
+
+* [Playground Link](/playground.html#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)
+
+### Description
+
+This YAML rule helps detect specific host and port configurations in your code. For example, it checks if the port is set to something other than 8000 or if a particular host is used. It provides an error message prompting you to update the configuration.
+
+### YAML
+
+```yaml
+id: detect-host-port
+message: You are using $HOST on Port $PORT, please change it to 8000
+severity: error
+rule:
+  any:
+    - pattern: |
+        port: $PORT
+    - pattern: |
+        host: $HOST
+```
+
+### Example
+
+<!-- highlight matched code in curly-brace {lineNum} -->
+```yaml {5,6}
+db:
+  username: root
+  password: root
+server:
+  host: 127.0.0.1
+  port: 8001
+```
+
+### Contributed by
+[rohitcoder](https://twitter.com/rohitcoder) on [Discord](https://discord.com/invite/4YZjf6htSQ).

website/catalog/yaml/index.md

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+# YAML
+
+This page curates a list of example ast-grep rules to check and to rewrite YAML code.
+
+<!--@include: ./find-key-value.md-->