docs(lua): move function docs to lua files

runtime/lua/vim/_meta/json.lua

@@ -0,0 +1,35 @@
+--- @meta
+
+--- @defgroup lua-json
+---
+--- @brief The \*vim.json\* module provides encoding and decoding of Lua objects to and
+--- from JSON-encoded strings. Supports |vim.NIL| and |vim.empty_dict()|.
+
+--- Decodes (or "unpacks") the JSON-encoded {str} to a Lua object.
+---
+--- - Decodes JSON "null" as |vim.NIL| (controllable by {opts}, see below).
+--- - Decodes empty object as |vim.empty_dict()|.
+--- - Decodes empty array as `{}` (empty Lua table).
+---
+--- Example:
+--- <pre>lua
+--- :lua vim.print(vim.json.decode('{"bar":[],"foo":{},"zub":null}'))
+--- --> { bar = {}, foo = vim.empty_dict(), zub = vim.NIL }
+--- </pre>
+--- Parameters: ~
+---   • {str}    Stringified JSON data.
+---   • {opts}   Options map keys:
+---              • luanil: { object: bool, array: bool }
+---                • `luanil.object=true` converts `null` in JSON objects to
+---                  Lua `nil` instead of `vim.NIL`.
+---                • `luanil.array=true` converts `null` in JSON arrays to Lua
+---                  `nil` instead of `vim.NIL`.
+--- @param str string
+--- @param opts? table<string, any>
+--- @return any
+function vim.json.decode(str, opts) end
+
+--- Encodes (or "packs") Lua object {obj} as JSON in a Lua string.
+--- @param obj any
+--- @return string
+function vim.json.encode(obj) end