Make `trim` interoperable with native Twig function

[chasegiunta]

[michaelrog]

Currently, Wordsmith's trim overrides Twig's core function. (This is intentional.) However, we could make them interoperable by adding some matching params to Wordsmith's trim function.

The new signature of our trim function would be something like:

public function trim($s, $characterMask = null, $side = 'both', $chars = null) : string

Pros:

• Affordance for anyone familiar with Twig's trim
• Prevent accidentally manifesting bugs in users' templates if they are already using Twig's trim when they install Wordsmith

Cons:

• Added complexity because we need to add conditional branches to Wordsmith's trim
• Redundancy w/ trimLeft and trimRight — Do we deprecate these?

Documentation options

1. Silent compatibility (i.e. Stringy params in documentation, Twig's params working silently as a bonus)
2. Deprecate the Stringy params in favor of documented compatibility with Twig's params
3. Document both param variations

I would welcome a PR to dev to address this.