[BUG] Don't color dot literal color names

- Colordots are generated for colors in inline code, such as `red`,
`rgb(255, 0, 124)`, `#ffaabb` and `hsl(124, 52%, 50%)`. However this
shouldn't be doon for literal color names as these can be too common
assiocated with non-color related stuff _and matches the behavior of
some other forge_.
- Move the regexes from bluemonday to Forgejo and do the checking
ourselves.
- Adds unit tests.
- Resolves https://codeberg.org/Codeberg/Community/issues/1510

modules/markup/markdown/goldmark.go

@@ -16,7 +16,6 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	giteautil "code.gitea.io/gitea/modules/util"
 
-	"github.com/microcosm-cc/bluemonday/css"
 	"github.com/yuin/goldmark/ast"
 	east "github.com/yuin/goldmark/extension/ast"
 	"github.com/yuin/goldmark/parser"
@@ -199,7 +198,7 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 			}
 		case *ast.CodeSpan:
 			colorContent := n.Text(reader.Source())
-			if css.ColorHandler(strings.ToLower(string(colorContent))) {
+			if matchColor(strings.ToLower(string(colorContent))) {
 				v.AppendChild(v, NewColorPreview(colorContent))
 			}
 		}