Add support for sub-indexes (#120)

<details>
<summary>Background</summary>

Sally renders two kinds of pages:

- packages: These are for packages defined in sally.yaml
  and any route under the package path.
- indexes: These list available packages.

The latter--indexes was previously only supported at '/', the root page.

This leads to a slight UX issue:
if you have a package with a / in its name (e.g. net/metrics):

- example.com/net/metrics gives you the package page
- example.com/ lists net/metrics
- However, example.com/net fails with a 404

</details>

This adds support for index pages on all parents of package pages.
Therefore, if example.com/net/metrics exists,
example.com/net will list all packages defined under that path.

Resolves #31

1 files changed, 3 insertions, 3 deletions

diff --git a/templates/index.html b/templates/index.html
index fa061f1..7ffc1a6 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -29,15 +29,15 @@
                 <div class="row">
                     <div class="five columns">
                         <span class="inline-header">Package:</span>
-                        {{ .ImportPath }}
+                        {{ .ModulePath }}
                     </div>
                     <div class="five columns">
                         <span class="inline-header">Source:</span>
                         <a href="//{{ .GitURL }}">{{ .GitURL }}</a>
                     </div>
                     <div class="two columns">
-                        <a href="//{{ .GodocHome }}">
-                            <img src="//pkg.go.dev/badge/{{ .ImportPath }}.svg" alt="Go Reference" />
+                        <a href="//{{ .DocURL }}">
+                            <img src="//pkg.go.dev/badge/{{ .ModulePath }}.svg" alt="Go Reference" />
                         </a>
                     </div>
                 </div>