Fix for #8777

Now filter name is trimmed and lowercased before evaluation for case
insensitive and whitespace trimemd check.

Signed-off-by: Oh Jinkyun <tintypemolly@gmail.com>
You meant filters instead of envfile right? I might be wrong, but I believe `ParseFlag` lives in the `filters` package and is solely used for that purpose, but that's worth verifying.