Fixed some non-normative inconsistencies

[hediet]

• "param" to "params" (both used equally often)
• "export interface" to "interface" (both used equally often)
• added missing "interface" keyword for InitializeResult interface

[msftclas]

Hi @hediet, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. Real humans will now evaluate your PR.

TTYL, MSBOT;