[Feature Request] Intersection types

まだ誰も着手していません。

I apologize if this request has been reported before, I couldn't find any.
It would be great to be able to explicitly differentiate between union types and intersection types
e.g.
```lua
--- @class A
local a = {foo = 1}

--- @class B
local b = {bar = "hello"}

--- @param aOrB A | B
--- @param aAndB A & B
local function someFunc(aOrB, aAndB) end

someFunc(a, a) -- no warning, but 2nd argument should give a warning

--- @param a A
local function someOtherFunc(a) end

--- @type A | B -- would prefer to use A & B and not have any warnings
local aAndB = {foo = 1, bar = "hello"}
someOtherFunc(aAndB) -- Cannot assign `A|B` to parameter `A`. - `B` cannot match `A` - Type `B` cannot match `A` Lua Diagnostics. (param-type-mismatch)
```

While it's possible to use an explicit class with inheritance as a workaround, this is not always viable, especially when using dynamic types with generics
```lua
--- @class C: A, B
local c = {foo = 1, bar = "hello"}
someOtherFunc(aAndB) -- no warning

-- not viable when using something like this
--- @generic T1, T2
--- @param tbl1 T1
--- @param tbl2 T2
--- @return T1 | T2 -- would like to use T1 & T2 instead to avoid the warnings
local function merge(tbl1, tbl2) end

someOtherFunc(merge(a, b)) -- Cannot assign `A|B` to parameter `A`. - `B` cannot match `A` - Type `B` cannot match `A` Lua Diagnostics. (param-type-mismatch)
```

The suggested syntax `A & B` for intersection types and `A | B` for union types matches several other languages, such as TypeScript and PHP.

Edit: another workaround is to enable [luals.github.io/wiki/settings#typeweakunioncheck](https://luals.github.io/wiki/settings/#typeweakunioncheck). This has its own downsides, but may be helpful for people trying to avoid the `param-type-mismatch` warnings

実装ファイルやテストは指定されていません。まず、Lua のアノテーションが共用体をどのように表現しているか、また param-type-mismatch 診断がそれらをどのように扱っているかを追跡し、次に A & B、A | B、汎用マージの例と挙動を比較します。交差アノテーションが示された誤警告を回避し、共用体が現在のチェックを維持すれば完了です。

索引モデルが issue の本文から書いたものです。