docs: add openapi references to new parameters protos

Co-Authored-By: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>

protoc-gen-openapiv2/options/openapiv2.proto

@@ -176,18 +176,24 @@ message Operation {
   // See: https://swagger.io/docs/specification/2-0/swagger-extensions/
   map<string, google.protobuf.Value> extensions = 13;
   // Custom parameters such as HTTP request headers.
+  // See: https://swagger.io/docs/specification/2-0/describing-parameters/
+  // and https://swagger.io/specification/v2/#parameter-object.
   Parameters parameters = 14;
 }
 
 // `Parameters` is a representation of OpenAPI v2 specification's parameters object.
+// See: https://swagger.io/specification/v2/#parameter-object
 message Parameters {
   // `Headers` is one or more HTTP header parameter.
+  // See: https://swagger.io/docs/specification/2-0/describing-parameters/#header-parameters
   repeated HeaderParameter headers = 1;
 }
 
 // `HeaderParameter` a HTTP header parameter.
+// See: https://swagger.io/specification/v2/#parameter-object
 message HeaderParameter {
-  // `Type` is a a supported HTTP type.
+  // `Type` is a a supported HTTP header type.
+  // See https://swagger.io/specification/v2/#parameterType.
   enum Type {
     UNKNOWN = 0;
     STRING = 1;
@@ -201,14 +207,15 @@ message HeaderParameter {
   // `Description` is a short description of the header.
   string description = 2;
   // `Type` is the type of the object. The value MUST be one of "string", "number", "integer", or "boolean". The "array" type is not supported.
+  // See: https://swagger.io/specification/v2/#parameterType.
   Type type = 3;
   // `Format` The extending format for the previously mentioned type.
   string format = 4;
   // `Required` indicates if the header is optional
   bool required = 5;
   // field 6 is reserved for 'items', but in OpenAPI-specific way.
   reserved 6;
-  // field 7 is reserved `Collection Format` Determines the format of the array if type array is used.
+  // field 7 is reserved `Collection Format`. Determines the format of the array if type array is used.
   reserved 7;
 }