`bs.unwrap`, `bs.string`, `bs.int` and `bs.as` cause warning 101 in interface files.

Nobody has claimed this yet.

According to https://bucklescript.github.io/docs/en/intro-to-external, we should add `[@bs.blabla]` in interface files but doing so with `bs.unwrap`, `bs.string`, `bs.int` or `bs.as` cause a warning 101 to be displayed in VSCode by RLS but it compiles without problem.
I tested it with RLS V1.7.4 and BS 5.2.1, 6.2.1, 7.0.1 and 7.0.2-dev.1 .
I made a demo repo here:
https://github.com/tsnobip/unwrap_warning_demo

In `node_modules/.lsp/debug.log` we can indeed find these warnings:
```
Read message
{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///Users/paul/code/unwrap_warning/src/Demo.rei","languageId":"reason","version":1,"text":"type foo;\n/**\n * this binding works as expected\n */ [@bs.val] external foo: foo = \"foo\";\n\n/**\n * this binding shows a warning at `bs.unwrap`\n * Warning 101: Unused BuckleScript attribute: bs.unwrap\n */\n[@bs.val]\nexternal bar: ([@bs.unwrap] [ | `Int(int) | `Str(string)]) => foo = \"bar\";\n\n/**\n * this binding shows a warning at the polymorphic variant\n * Warning 103: BuckleScript FFI warning: Here a OCaml polymorphic variant type\n * passed into JS, probably you forgot annotations like `[@bs.int]` or `[@bs.string]`\n */\n// [@bs.val]\n// external baz: [ | `Int(int) | `Str(string)] => foo = \"baz\";\n\n/**\n * this binding shows a warning at `bs.string`\n * Warning 101: Unused BuckleScript attribute: bs.unwrap\n * and another one at `bs.as\n * Warning 101: Unused BuckleScript attribute: bs.unwrap\n * Removing `bs.as` raises the following error:\n * The implementation src/Demo.re\n does not match the interface src/demo-Unwrapwarning.cmi:\n Values do not match:\n [@bs...] external barString: [ `Bar | `Foo ] => foo = \"bar\"\n is not included in\n [@bs...] external barString: [ `Bar | `Foo ] => foo = \"bar\"\n File \"src/Demo.re\", line 10, characters 0-91:\n Actual declaration\n */\n[@bs.val]\nexternal barString: ([@bs.string] [ | `Foo | [@bs.as \"baz\"] `Bar]) => foo = \"bar\";\n\n/**\n * this binding shows a warning at the polymorphic variant\n * Warning 103: BuckleScript FFI warning: Here a OCaml polymorphic variant type\n * passed into JS, probably you forgot annotations like `[@bs.int]` or `[@bs.string]`\n * Uncommenting this binding would raise an error:\n * Some fatal warnings were triggered (1 occurrences)\n */\n// [@bs.val]\n// external bazString: [ | `Foo | [@bs.as \"baz\"] `Bar] => foo = \"baz\";\n\n/**\n * this binding shows a warning at `bs.int`\n * Warning 101: Unused BuckleScript attribute: bs.unwrap\n * and another one at `bs.as\n * Warning 101: Unused BuckleScript attribute: bs.unwrap\n */\n[@bs.val]\nexternal barInt: ([@bs.int] [ | `Foo | [@bs.as 10] `Bar]) => foo = \"bar\";\n\n/**\n * this binding shows a warning at the polymorphic variant\n * Warning 103: BuckleScript FFI warning: Here a OCaml polymorphic variant type\n * passed into JS, probably you forgot annotations like `[@bs.int]` or `[@bs.string]`\n * Uncommenting this binding would raise an error:\n * Some fatal warnings were triggered (1 occurrences)\n */\n// [@bs.val]\n// external bazInt: [ | `Foo | [@bs.as 10] `Bar] => foo = \"baz\";\n"}}}
```

Start with the demo repository and reproduce the warnings in the Reason interface example, then inspect node_modules/.lsp/debug.log and the referenced src/Demo.re declarations. Done means the bs.unwrap, bs.string, bs.int, and bs.as annotations no longer produce the reported warning 101 messages while the interface still matches its implementation.

Written by the indexing model from the issue text.