feat: add $$operation$$ file template

docs/file-templates.md

@@ -6,6 +6,7 @@ weight: 140
 It is possible to generate files for each specific object in your AsyncAPI documentation. For example, you can specify a filename like `$$channel$$.js` to generate a file for each channel defined in your AsyncAPI. The following file-template names and extra variables in them are available:
 
    - `$$channel$$`, within the template-file you have access to two variables [`channel`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#channel) and [`channelName`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#channels). Where the `channel` contains the current channel being rendered.
+   - `$$operation$$`, within the template-file you have access to two variables [`operation`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#operation) and [`operationName`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#operations). Where the `operation` contains the current operation being rendered.
    - `$$message$$`, within the template-file you have access to two variables [`message`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#message) and [`messageName`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#message). Where `message` contains the current message being rendered.
    - `$$schema$$`, within the template-file you have access to two variables [`schema`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#schema) and [`schemaName`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#schema). Where `schema` contains the current schema being rendered. Only schemas from [Components object](https://www.asyncapi.com/docs/reference/specification/latest#componentsObject) are used. 
    - `$$everySchema$$`, within the template-file you have access to two variables [`schema`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#schema) and [`schemaName`](https://github.com/asyncapi/parser-api/blob/master/docs/api.md#schemas). Where `schema` contains the current schema being rendered. Every [Schema object](https://www.asyncapi.com/docs/specifications/2.0.0/#schemaObject) from the entire AsyncAPI file is used.

lib/generator.js

@@ -731,6 +731,7 @@ class Generator {
         objectSchema: convertCollectionToObject(asyncapiDocument.schemas().all().filter(schema => schema.type() === 'object'), 'id'),
         parameter: convertMapToObject(this.getAllParameters(asyncapiDocument)),
         everySchema: convertCollectionToObject(asyncapiDocument.schemas().all(), 'id'),
+        operation: convertCollectionToObject(asyncapiDocument.operations().all(), 'id'),
       };
     } else {
       const objectSchema = {};
@@ -743,6 +744,7 @@ class Generator {
         objectSchema,
         parameter: convertMapToObject(this.getAllParameters(asyncapiDocument)),
         everySchema: convertMapToObject(asyncapiDocument.allSchemas()),
+        operation: convertCollectionToObject(asyncapiDocument.allOperations()),
       };
     }