feat(gnoweb): added link to readme if present (gnolang#2461)

Added a link to the `README.md` file of the realm if it exists 

![image](https://github.com/gnolang/gno/assets/68433935/8259ebd7-9a15-4647-9280-80618f870fcc)
To allow for quicker access while browsing gnoweb

This should solve gnolang#2458

<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
- [ ] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

---------

Co-authored-by: Lee ByeongJun <lbj199874@gmail.com>
Co-authored-by: Guilhem Fanton <8671905+gfanton@users.noreply.github.com>

gno.land/pkg/gnoweb/gnoweb.go

@@ -1,6 +1,7 @@
 package gnoweb
 
 import (
+	"bytes"
 	"embed"
 	"encoding/json"
 	"errors"
@@ -335,6 +336,15 @@ func handleRealmRender(logger *slog.Logger, app gotuna.App, cfg *Config, w http.
 			return
 		}
 	}
+
+	dirdata := []byte(rlmpath)
+	dirres, err := makeRequest(logger, cfg, qFileStr, dirdata)
+	if err != nil {
+		writeError(logger, w, err)
+		return
+	}
+	hasReadme := bytes.Contains(append(dirres.Data, '\n'), []byte("README.md\n"))
+
 	// linkify querystr.
 	queryParts := strings.Split(querystr, "/")
 	pathLinks := []pathLink{}
@@ -354,6 +364,7 @@ func handleRealmRender(logger *slog.Logger, app gotuna.App, cfg *Config, w http.
 	tmpl.Set("PathLinks", pathLinks)
 	tmpl.Set("Contents", string(res.Data))
 	tmpl.Set("Config", cfg)
+	tmpl.Set("HasReadme", hasReadme)
 	tmpl.Render(w, r, "realm_render.html", "funcs.html")
 }
 

gno.land/pkg/gnoweb/views/realm_render.html

@@ -16,6 +16,9 @@
           {{- end -}}
         </span>
         <span id="realm_links">
+          {{ if .Data.HasReadme }}
+          <a href="/r/{{ .Data.RealmName }}/README.md">[readme]</a>
+          {{ end }}
           <a href="/r/{{ .Data.RealmName }}/">[source]</a>
           <a href="/r/{{ .Data.RealmName }}?help">[help]</a>
         </span>