chore(docs): add docs

doc/gopher.nvim.txt

@@ -13,6 +13,7 @@ Table of Contents
   Config ................................................ |gopher.nvim-config|
   Commands ............................................ |gopher.nvim-commands|
   Modify struct tags ............................... |gopher.nvim-struct-tags|
+  json2go .............................................. |gopher.nvim-json2go|
   Auto implementation of interface methods ................ |gopher.nvim-impl|
   Generating unit tests boilerplate .................... |gopher.nvim-gotests|
   Iferr .................................................. |gopher.nvim-iferr|
@@ -69,6 +70,7 @@ or use `require("gopher").install_deps()` if you prefer lua api.
       gotests = "gotests",
       impl = "impl",
       iferr = "iferr",
+      json2go = "json2go",
     },
     ---@class gopher.ConfigGotests
     gotests = {
@@ -96,12 +98,24 @@ or use `require("gopher").install_deps()` if you prefer lua api.
       ---@type string|nil
       option = nil,
     },
+    ---@class gopher.ConfigIfErr
     iferr = {
       -- choose a custom error message, nil to use default
       -- e.g: `message = 'fmt.Errorf("failed to %w", err)'`
       ---@type string|nil
       message = nil,
     },
+    ---@class gopher.ConfigJson2Go
+    json2go = {
+      -- command used to open interactive input.
+      -- e.g: `split`, `botright split`, `tabnew`
+      interactive_cmd = "vsplit",
+
+      -- name of autogenerated struct, if nil none, will the default one of json2go.
+      -- e.g: "MySuperCoolName"
+      ---@type string|nil
+      type_name = nil,
+    },
   }
 <
 Class ~
@@ -157,6 +171,42 @@ Example:
    }
 <
 
+==============================================================================
+------------------------------------------------------------------------------
+                                                           *gopher.nvim-json2go*
+
+Convert json to go type annotations.
+
+Usage ~
+
+`:GoJson` opens a temporary buffer where you can paste or write JSON.
+Saving the buffer (`:w` or `:wq`) automatically closes it and inserts the
+generated Go struct into the original buffer at the cursor position.
+
+Alternatively, you can pass JSON directly as an argument:
+>vim
+   :GoJson {"name": "Alice", "age": 30}
+<
+------------------------------------------------------------------------------
+                                                           *json2go.transform()*
+                        `json2go.transform`({json_str})
+
+Parameters ~
+{json_str} `(string)` Json string that is going to be converted to go type.
+Return ~
+`(string)` `(optional)` Go type, or nil if failed.
+
+------------------------------------------------------------------------------
+                                                             *json2go.json2go()*
+                         `json2go.json2go`({json_str})
+Converts json string to go type, and puts result under the cursor. If
+[json_str] is nil, will open an interactive prompt (with cmd set in
+config).
+
+Parameters ~
+{json_str} `(optional)` `(string)`
+
+
 ==============================================================================
 ------------------------------------------------------------------------------
                                                               *gopher.nvim-impl*