tailwindcss-language-server: Give main $out/bin +x permission

The install phase was changed in
https://github.com/NixOS/nixpkgs/pull/363636 and the executable flag is
missing. This causes errors like these when loading from Neovim:

```
...-unwrapped-0.10.2/share/nvim/runtime/lua/vim/lsp/rpc.lua:800:
Spawning language server with cmd: `{ "tailwindcss-language-server",
"--stdio" }` failed with error message:
...-unwrapped-0.10.2/share/nvim/runtime /lua/vim/_system.lua:244:
EACCES: permission denied
```

This is what the file looks like in the Nix store:

```
ls -la
/nix/store/<hash>-tailwindcss-language-server-0.0.27/lib/tailwindcss-language-server/packages/tailwindcss-language-server/bin/tailwindcss-language-server
~/Development/nixpkgs λ ls -la
/nix/store/<hash>-tailwindcss-language-server-0.0.27/lib/tailwindcss-language-server/packages/tailwindcss-language-server/bin/tailwindcss-language-server
.r--r--r-- 4,8M root  1 Jan  1970
/nix/store/<hash>-tailwindcss-language-server-0.0.27/lib/tailwindcss-language-server/packages/tailwindcss-language-server/bin/tailwindcss-language-server
```

0 files changed, 0 insertions, 0 deletions