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())

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

@@ -25,7 +25,7 @@ func (e *ImageElement) Render(w io.Writer, ctx RenderContext) error {
 	}
 	if len(e.URL) > 0 {
 		el := &BaseElement{
-			Token:  resolveRelativeURL(e.BaseURL, e.URL),
+			Token:  resolveURL(e.BaseURL, e.URL),
 			Prefix: " ",
 			Style:  ctx.options.Styles.Image,
 		}

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

@@ -64,7 +64,7 @@ func (e *LinkElement) Render(w io.Writer, ctx RenderContext) error {
 		}
 
 		el := &BaseElement{
-			Token:  resolveRelativeURL(e.BaseURL, e.URL),
+			Token:  resolveURL(e.BaseURL, e.URL),
 			Prefix: pre,
 			Style:  style,
 		}

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

@@ -3,9 +3,9 @@ package ansi
 import (
 	"io"
 	"net/url"
-	"strings"
 
 	"github.com/muesli/termenv"
+	east "github.com/yuin/goldmark-emoji/ast"
 	"github.com/yuin/goldmark/ast"
 	astext "github.com/yuin/goldmark/extension/ast"
 	"github.com/yuin/goldmark/renderer"
@@ -72,13 +72,16 @@ func (r *ANSIRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
 	reg.Register(astext.KindFootnote, r.renderNode)
 	reg.Register(astext.KindFootnoteList, r.renderNode)
 	reg.Register(astext.KindFootnoteLink, r.renderNode)
-	reg.Register(astext.KindFootnoteBackLink, r.renderNode)
+	reg.Register(astext.KindFootnoteBacklink, r.renderNode)
 
 	// checkboxes
 	reg.Register(astext.KindTaskCheckBox, r.renderNode)
 
 	// strikethrough
 	reg.Register(astext.KindStrikethrough, r.renderNode)
+
+	// emoji
+	reg.Register(east.KindEmoji, r.renderNode)
 }
 
 func (r *ANSIRenderer) renderNode(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
@@ -145,7 +148,7 @@ func isChild(node ast.Node) bool {
 	return false
 }
 
-func resolveRelativeURL(baseURL string, rel string) string {
+func resolveURL(baseURL string, rel string) string {
 	u, err := url.Parse(rel)
 	if err != nil {
 		return rel
@@ -153,7 +156,6 @@ func resolveRelativeURL(baseURL string, rel string) string {
 	if u.IsAbs() {
 		return rel
 	}
-	u.Path = strings.TrimPrefix(u.Path, "/")
 
 	base, err := url.Parse(baseURL)
 	if err != nil {