tawk: ship first-class TypeScript types (4+ year community gap)

[productdevbook]

`tawk-messenger-react#13` open since 2022. No first-party types. Community ships hand-rolled `.d.ts` shims.

Evidence

• `Incompatible with typescript tawk/tawk-messenger-react#13` Incompatible with typescript tawk/tawk-messenger-react#13
• `Add typescript type definition file tawk/tawk-messenger-react#7` Add typescript type definition file tawk/tawk-messenger-react#7
• `Hope to support typescript tawk/tawk-messenger-vue-3#7` Hope to support typescript tawk/tawk-messenger-vue-3#7

Tasks

• Full typings for `window.Tawk_API`: `setAttributes`, `addEvent`, `visitor`, `showWidget`, `hideWidget`, `maximize`, `minimize`, `toggle`, `popup`, `endChat`, `onLoad`, `onStatusChange`, `onChatMaximized`, `onChatMinimized`, `onChatHidden`, `onChatStarted`, `onChatEnded`, `onChatMessageVisitor`, `onChatMessageAgent`, `onChatMessageSystem`, `onAgentJoinChat`, `onAgentLeaveChat`, `onChatSatisfaction`, `onVisitorNameChanged`, `onFileUpload`, `onTagsUpdated`, `onUnreadCountChanged`, `login`, `logout`, `switchWidget`
• Callback payload types (not `any` or `Function`)

[productdevbook]

Implemented in this commit