Instead of waiting for a good time to switch the `Map` implementation,
I've decided to just offer two implementations: one for Go versions
before 1.18, and one for 1.18 and onwards. This is achieved using build
tags in the source files.
This is obviously a breaking change for consumers of this library that
use Go 1.18 and onwards.
See #88
There were a lot of elements previously, like `Em`, `H1`, and a lot more, that took a string as the first argument previously. This was weird when you wanted to mix elements to output html like `<strong><em>…</em></strong>` or `<h1>Something <em>something</em> something</h1>`. gomponents is not an HTML validator, so I want people to be able to use elements however they please, also without text content.
This also means that all elements now have the same API.
`a`, `form`, `img`, `input`, `label`, `option`, `progress`, `select`, and `textarea` are now just regular elements (without helper parameters), because:
- Sometimes the use case doesn't fit (`a` as anchor without href, for example)
- There's no reason these are special among the others, so streamlining them makes sense
Also added new attributes `action`, `alt`, `for`, `method` that I had somehow missed.
This makes it easier to use dot-imports.
Also updated the readme and examples with new usage, and move the `Classes` helper into the `components` package.
The Render function has been changed to take a `Writer` instead of returning a string. This makes it possible to generate documents without having the whole content in memory.
This also removes the `gomponents.Write` function, which is now redundant.
Furthermore, the `el.Document` function has been changed to only take one child, as multiple children never make sense for it. (It's not even a child, more a sibling.)
