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/alecthomas/chroma/lexers/t/toml.go

@@ -22,7 +22,7 @@ var TOML = internal.Register(MustNewLexer(
 			{`[+-]?[0-9](_?\d)*`, LiteralNumberInteger, nil},
 			{`"(\\\\|\\"|[^"])*"`, StringDouble, nil},
 			{`'(\\\\|\\'|[^'])*'`, StringSingle, nil},
-			{`[.,=\[\]]`, Punctuation, nil},
+			{`[.,=\[\]{}]`, Punctuation, nil},
 			{`[^\W\d]\w*`, NameOther, nil},
 		},
 	},