docs: add envoy lib examples (#201)

Signed-off-by: Charles-Edouard Brétéché <charles.edouard@nirmata.com>

website/docs/cel-extensions/envoy.md

@@ -28,7 +28,9 @@ envoy.Allowed() -> <OkHttpResponse>
 
 #### Example
 
-TODO
+```
+envoy.Allowed()
+```
 
 ### envoy.Denied
 
@@ -42,7 +44,9 @@ envoy.Denied(<int> code) -> <DeniedHttpResponse>
 
 #### Example
 
-TODO
+```
+envoy.Denied(401)
+```
 
 ### envoy.Response
 
@@ -62,7 +66,19 @@ envoy.Response(<DeniedHttpResponse> denied) -> <CheckResponse>
 
 #### Example
 
-TODO
+```
+// ok
+envoy.Response(0)
+
+// permission denied
+envoy.Response(7)
+```
+```
+envoy.Response(envoy.Allowed())
+```
+```
+envoy.Response(envoy.Denied(401))
+```
 
 ### envoy.Null
 
@@ -76,7 +92,9 @@ envoy.Null() -> <CheckResponse>
 
 #### Example
 
-TODO
+```
+envoy.Null()
+```
 
 ### envoy.Header
 
@@ -90,7 +108,9 @@ envoy.Header(<string> key, <string> value) -> <HeaderValueOption>
 
 #### Example
 
-TODO
+```
+envoy.Header("foo", "bar")
+```
 
 ### WithBody
 
@@ -104,12 +124,16 @@ This function sets the body of a `<DeniedHttpResponse>` object.
 
 #### Example
 
-TODO
+```
+envoy.Denied(401).WithBody("Unauthorized Request")
+```
 
 ### WithHeader
 
-This function adds a `<HeaderValueOption>` when the request is sent upstream by Envoy, in the case of an `OkHttpResponse`.
-This function adds a `<HeaderValueOption>` when the response is sent downstream by Envoy, in the case of a `DeniedHttpResponse`.
+This function adds a `<HeaderValueOption>`:
+
+- When the request is sent upstream by Envoy, in the case of an `<OkHttpResponse>`.
+- When the response is sent downstream by Envoy, in the case of a `<DeniedHttpResponse>`.
 
 #### Signature and overloads
 
@@ -128,7 +152,18 @@ This function adds a `<HeaderValueOption>` when the response is sent downstream
 
 #### Example
 
-TODO
+```
+envoy.Allowed().WithHeader(envoy.Header("foo", "bar"))
+```
+```
+envoy.Allowed().WithHeader("foo", "bar")
+```
+```
+envoy.Denied(401).WithHeader(envoy.Header("foo", "bar"))
+```
+```
+envoy.Denied(401).WithHeader("foo", "bar")
+```
 
 ### WithoutHeader
 
@@ -142,7 +177,9 @@ This function marks a header to be removed when the request is sent upstream by
 
 #### Example
 
-TODO
+```
+envoy.Allowed().WithoutHeader("foo")
+```
 
 ### WithResponseHeader
 
@@ -159,7 +196,12 @@ This function adds a `<HeaderValueOption>` when the response is sent downstream
 
 #### Example
 
-TODO
+```
+envoy.Allowed().WithResponseHeader(envoy.Header("foo", "bar"))
+```
+```
+envoy.Allowed().WithResponseHeader("foo", "bar")
+```
 
 ### WithQueryParam
 
@@ -173,7 +215,12 @@ This function adds a `<QueryParameter>` to be added when the request is sent ups
 
 #### Example
 
-TODO
+```
+envoy.Allowed().WithQueryParam(envoy.config.core.v3.QueryParameter{
+    key: "foo",
+    bar: "bar"
+})
+```
 
 ### WithoutQueryParam
 
@@ -187,7 +234,9 @@ This function marks a query parameter to be removed when the request is sent ups
 
 #### Example
 
-TODO
+```
+envoy.Allowed().WithoutQueryParam("foo")
+```
 
 ### KeepEmptyValue
 
@@ -204,7 +253,12 @@ This function sets the `keep_empty_value` field of an `<HeaderValueOption>` obje
 
 #### Example
 
-TODO
+```
+envoy.Header("foo", "bar").KeepEmptyValue()
+```
+```
+envoy.Header("foo", "bar").KeepEmptyValue(true)
+```
 
 ### Response
 
@@ -221,7 +275,12 @@ This function creates a `<CheckResponse>` object from an `<OkHttpResponse>` or `
 
 #### Example
 
-TODO
+```
+envoy.Allowed().Response()
+```
+```
+envoy.Denied(401).Response()
+```
 
 ### WithMessage
 
@@ -235,7 +294,12 @@ This function sets the `status.message` field of a `<CheckResponse>` object.
 
 #### Example
 
-TODO
+```
+envoy.Allowed().Response().WithMessage("hello world!")
+```
+```
+envoy.Denied(401).Response().WithMessage("hello world!")
+```
 
 ### WithMetadata
 
@@ -249,4 +313,9 @@ This function sets the `dynamic_metadata` field of a `<CheckResponse>` object.
 
 #### Example
 
-TODO
+```
+envoy.Allowed().Response().WithMetadata({ "foo": "bar" })
+```
+```
+envoy.Denied(401).Response().WithMetadata({ "foo": "bar" })
+```