Add media proxy documentation

releases/0.5.0.md

@@ -114,6 +114,34 @@ It is possible to migrate to postgres after first upgrading to 0.5. This is also
 
 ### Media Proxy
 
+pict-rs 0.5 supports caching media, and purging cached media after it is no longer necessary to
+keep. This behavior is accessed with pict-rs' new `proxy` query parameter at the `/image/original`
+endpoint, and the `/image/process.{ext}` endpoint. By passing the URL to an image to the `proxy`
+parameter, you can instruct pict-rs to download the media from that URL and cache it locally before
+serving it, or a processed version of it. The proxied media is stored for a configurable time limit,
+which resets on each access to the proxied media.
+
+This value can be configured as follows
+
+In the configuration file
+```toml
+[media.retention]
+proxy = "7d" # units available are "m" for minutes, "h" for hours, "d" for days, and "y" for years
+```
+
+With environment variables
+```bash
+PICTRS__MEDIA__RETENTION__PROXY=7d
+```
+
+On the commandline
+```bash
+pict-rs run --media-retention-proxy 7d
+```
+
+More documentation can be found in the [pict-rs readme](https://git.asonix.dog/asonix/pict-rs#api)
+and in the example [pict-rs.toml](https://git.asonix.dog/asonix/pict-rs/src/branch/main/pict-rs.toml).
+
 
 ### Improved Animation Support