After activation, write-good lints all filetypes and languages

[JPRuskin]

Issue: After activation (by opening a markdown language document) this extension lints all documents - including code, etc.

Replication:

• Install vscode-write-good to VS Code
• Open a markdown document, see that linting is occurring
• Switch to another document (i.e. a script) and see that linting is still occurring

Expected Behavior: Lint only markdown (or plaintext) documents.

[TravisTheTechie]

Released in v0.0.6, https://marketplace.visualstudio.com/items?itemName=travisthetechie.write-good-linter#overview