Constant constructor with required options.
Source
const Options( {this.rawHtml: true, this.smartPunctuation: false, this.fencedCodeAttributes: false, this.headingAttributes: false, this.inlineCodeAttributes: false, this.linkAttributes: false, this.strikeout: false, this.subscript: false, this.superscript: false, this.texMathDollars: false, this.texMathSingleBackslash: false, this.texMathDoubleBackslash: false, this.rawTex: false, this.pipeTables: false, this.inlineTexMathClasses: const <String>['math', 'inline'], this.displayTexMathClasses: const <String>['math', 'display'], this.linkResolver: defaultLinkResolver});