[meta] Basic impl of `String.prototype`

[CanadaHonk]

• [x] String.prototype.anchor()
• [X] String.prototype.at()
• [X] String.prototype.big()
• [X] String.prototype.blink()
• [X] String.prototype.bold()
• [X] String.prototype.charAt()
• [X] String.prototype.charCodeAt()
• [x] String.prototype.codePointAt()
• [x] String.prototype.concat()
• [X] String.prototype.endsWith()
• [X] String.prototype.fixed()
• [x] String.prototype.fontcolor()
• [x] String.prototype.fontsize()
• [X] String.prototype.includes()
• [X] String.prototype.indexOf()
• [X] String.prototype.isWellFormed()
• [X] String.prototype.italics()
• [X] String.prototype.lastIndexOf()
• [x] String.prototype.link()
• [x] String.prototype.localeCompare()
• [ ] String.prototype.match()
• [ ] String.prototype.matchAll()
• [ ] String.prototype.normalize()
• [X] String.prototype.padEnd()
• [X] String.prototype.padStart()
• [x] String.prototype.repeat()
• [ ] String.prototype.replace()
• [ ] String.prototype.replaceAll()
• [X] String.prototype.search()
• [X] String.prototype.slice()
• [X] String.prototype.small()
• [x] String.prototype.split()
• [X] String.prototype.startsWith()
• [X] String.prototype.strike()
• [X] String.prototype.sub()
• [X] String.prototype.substr()
• [X] String.prototype.substring()
• [X] String.prototype.sup()
• [x] String.prototype.toLocaleLowerCase()
• [x] String.prototype.toLocaleUpperCase()
• [X] String.prototype.toLowerCase()
• [X] String.prototype.toString()
• [X] String.prototype.toUpperCase()
• [x] String.prototype.toWellFormed()
• [X] String.prototype.trim()
• [X] String.prototype.trimEnd()
• [X] String.prototype.trimStart()
• [X] String.prototype.valueOf()