fix: update stac viewer endpoint value (#311)

### Issue
#291

### What?

- Updated the endpoint value for the STAC viewer in order to properly
render the collections on the webpage.
- Added a PR template so that all new PRs will have a template for
reference

### Why?

- The endpoint is https://dev.openveda.cloud/collections which is
incorrect which causes the collections filter to fail in the STAC
viewer.


https://github.com/NASA-IMPACT/veda-backend/assets/12633533/b272fb4c-23a9-41c2-8ce8-925c6760231a


### Testing?

- I didn't locally deploy or anything but here is [the working
collections link](https://dev.openveda.cloud/api/stac/collections)

### Notes
- I think we could technically also update
https://github.com/NASA-IMPACT/veda-backend/blob/develop/stac_api/runtime/src/app.py#L79
to be:
```{"request": request, "endpoint": str(request.url).replace("/index.html", "/api/stac")},``` if that's preferred

.github/pull_request_template.md

@@ -0,0 +1,17 @@
+
+### Issue
+
+Link to relevant GitHub issue
+
+### What?
+
+- Description of the changes made
+
+### Why?
+
+- Description of why the changes were made
+
+### Testing?
+
+- Relevant testing details
+

stac_api/runtime/src/app.py

@@ -74,9 +74,10 @@
 @app.get("/index.html", response_class=HTMLResponse)
 async def viewer_page(request: Request):
     """Search viewer."""
+    path = api_settings.root_path or ""
     return templates.TemplateResponse(
         "stac-viewer.html",
-        {"request": request, "endpoint": str(request.url).replace("/index.html", "")},
+        {"request": request, "endpoint": str(request.url).replace("/index.html", path)},
         media_type="text/html",
     )