Expose EncodedTokenAttributes in main.ts

[tobil4sk]

Without this, there is no way to use IGrammar.tokenizeLine2 without redefining the EncodedTokenDataConsts and reimplementing the functions.

See for example: https://github.com/microsoft/vscode/blob/8810d514c7452ce912bd9bc6f79a3429cc55dcdd/src/vs/editor/common/encodedTokenAttributes.ts#L101-L103