Allow trailing spaces

[jarda-svoboda]

This PR slightly changes behavior of the Default parser's placeholders. In previous versions, all trailing spaces have been trimmed. This change will result in this behavior:

{{ undefined_key; default: Default value; }}
// => 'Default value'

{{ undefined_key; default: Default value ; }}
// => 'Default value '

{{undefined_key; default: Default value}}
// => 'Default value'

{{ undefined_key; default: Default value }}
// => 'Default value '

• Edit whitespace trimming
• Update tests

Closes sveltekit-i18n/lib#111