%N renders the fractional part of the second. The milliseconds returned by
getMilliseconds() are the three most significant digits of that fraction and
must be zero-padded to three digits before use, otherwise sub-100ms values
lose their leading zeros:
50ms => strftime("%N") returned "500000000", expected "050000000"
5ms => strftime("%3N") returned "500", expected "005"
Pad the milliseconds to three digits before slicing to the requested width.
Ruby/Shopify `slice` returns nil (rendered as an empty string or array) when
the begin offset falls outside the negative range or when the length is
negative. liquidjs forwarded the adjusted indices straight to
Array/String.prototype.slice, whose own negative-index handling produced
non-empty, incorrect output:
{{ "hello" | slice: -10, 2 }} => "he" (expected "")
{{ "Liquid" | slice: 1, -2 }} => "iqui" (expected "")
Guard the adjusted begin and the length before slicing.
The `modulo` filter used JavaScript's `%` (truncated remainder, sign
follows the dividend). Shopify/Ruby Liquid uses floored modulo, where the
result takes the sign of the divisor. Since liquidjs advertises Shopify
compatibility, negative operands produced the wrong sign.
Use `((v % arg) + arg) % arg` to match Ruby's `%`. Positive-operand
results are unchanged.
