Documentation is a mess

[Destroy666x]

Here are some obvious issues I spotted:

• https://nest-modules.github.io/mailer/ isn't even up-to-date with

  mailer/docs/mailer.md

  Line 488 in 248e829

  You can use [mjml](https://mjml.io/) to create responsive emails with the `MjmlAdapter` adapter. The templates themselves still need to be pre-rendered with pug, handlebars or ejs.

  - MJML isn't mentioned
• Lots of options are undocumented and some of the documented ones are unclear, e.g. why does MJMLAdapter need inlineCssEnabled to be false? How to use partials, other than configuring them? Can you even use Handlebars partials with MJML? 0 explantation.

[juandav]

Addressed in branch fix/multiple-issues-and-dependency-updates. Documentation improvements include:

• Added Liquid adapter configuration examples
• Clarified MJML setup requirements (inlineCssEnabled: false is required, others param is optional)
• Added multiple transporters documentation (transports config, addTransporter(), verifyAllTransporters())
• Added pnpm installation instructions
• Added liquidjs to the template engine installation list