Basic code intel: unescaped `.` matches more file extensions than intended

Created by: chrismwendt

I think I didn't properly escape the . in basic-code-intel's search query, so the file:.c$ filter also matches .pylintrc in addition to .c:

https://sourcegraph.com/github.com/sourcegraph/sourcegraph-basic-code-intel@b742102e382999749fea2fb17a44befa9f78ddb3/-/blob/package/src/handler.ts#L35

See https://sourcegraph.slack.com/archives/CHXHX7XAS/p1573328358329500