[240] Accept dates without time

[bkiers]

Ruby accepts dates without time:

require 'liquid'

tests = [
  '{{ "2022-10-13 12:06:04" | date: "%m-%e" }}',
  '{{ "2022-10-13" | date: "%m-%e" }}',
  '{{ "13-10-2022" | date: "%m-%e" }}'
]

tests.each { |test|
  @template = Liquid::Template.parse(test)
  puts @template.render
}

results in:

10-13
10-13
10-13

With this change, Liqp produces the same output.

Fixes #240