fix(parser): make parse_request handle request TS nodes

Problem:

Placing cursor between a request method and a uri and then invoking
`:Rest run` causes the node to be incorrectly parsed leading to an error.

See the following where the column above the caret (^) denotes the
cursor position:

```
GET https://google.com
   ^ cursor above caret
```

Running this will cause an error. This is because the
`parser.parse_request` method cannot handle Treesitter nodes of type
`request`.

Solution:

Make the `parser.parse_request` function handle Treesitter nodes of type
`request` by recursively calling itself on the `request` node and taking
that output when it finds a `request` node.

lua/rest-nvim/parser/init.lua

@@ -221,6 +221,8 @@ function parser.parse_request(children_nodes, variables)
     elseif node_type == "http_version" then
       local http_version = assert(get_node_text(node, 0))
       request.http_version = http_version:gsub("HTTP/", "")
+    elseif node_type == "request" then
+      request = parser.parse_request(traverse_request(node), variables)
     end
   end