docs: improve/add documentation of Lua types

- Added `@inlinedoc` so single use Lua types can be inlined into the
  functions docs. E.g.

  ```lua
  --- @class myopts
  --- @inlinedoc
  ---
  --- Documentation for some field
  --- @field somefield integer

  --- @param opts myOpts
  function foo(opts)
  end
  ```

  Will be rendered as

  ```
  foo(opts)

    Parameters:
      - {opts} (table) Object with the fields:
               - somefield (integer) Documentation
                 for some field
  ```

- Marked many classes with with `@nodoc` or `(private)`.
  We can eventually introduce these when we want to.

runtime/lua/vim/_meta/lpeg.lua

@@ -21,6 +21,7 @@ error('Cannot require a meta file')
 
 vim.lpeg = {}
 
+--- @nodoc
 --- @class vim.lpeg.Pattern
 --- @operator unm: vim.lpeg.Pattern
 --- @operator add(vim.lpeg.Pattern): vim.lpeg.Pattern
@@ -167,6 +168,7 @@ function vim.lpeg.S(string) end
 --- @return vim.lpeg.Pattern
 function vim.lpeg.V(v) end
 
+--- @nodoc
 --- @class vim.lpeg.Locale
 --- @field alnum userdata
 --- @field alpha userdata