Detect markdown line width, resolve relative URLs (#332)

~~this is semi-blocked by https://github.com/charmbracelet/glamour/pull/96, but behaviour isn't really worse than the previous behaviour (most links work, some are still broken)~~

#### testcase for link resolver
```
tea pr 332
tea checkout 332 && make install && tea pr 332
```

- [rel](./332)
- [abs](/gitea/tea/pulls/332)
- [full](https://gitea.com/gitea/tea/pulls/332)

Co-authored-by: Norwin Roosen <git@nroo.de>
Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/332
Reviewed-by: 6543 <6543@obermui.de>
Reviewed-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Norwin <noerw@noreply.gitea.io>
Co-committed-by: Norwin <noerw@noreply.gitea.io>

vendor/github.com/charmbracelet/glamour/ansi/elements.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"strings"
 
+	east "github.com/yuin/goldmark-emoji/ast"
 	"github.com/yuin/goldmark/ast"
 	astext "github.com/yuin/goldmark/extension/ast"
 )
@@ -375,6 +376,14 @@ func (tr *ANSIRenderer) NewElement(node ast.Node, source []byte) Element {
 	case ast.KindTextBlock:
 		return Element{}
 
+	case east.KindEmoji:
+		n := node.(*east.Emoji)
+		return Element{
+			Renderer: &BaseElement{
+				Token: string(n.Value.Unicode),
+			},
+		}
+
 	// Unknown case
 	default:
 		fmt.Println("Warning: unhandled element", node.Kind().String())