put rendered images into the repo

proposals/images/2846-receiving-current.mermaid

@@ -0,0 +1,14 @@
+sequenceDiagram
+  participant C as Client
+  participant S as Server
+  participant O as Origin
+  C->>S: req file
+  activate S
+  opt fetch file
+    S->>O: req file
+    activate O
+    O-->>S: serve file
+    deactivate O
+  end
+  S-->>C: serve file
+  deactivate S

proposals/images/2846-receiving-proposed.mermaid

@@ -0,0 +1,21 @@
+sequenceDiagram
+  participant C as Client
+  participant S as Server
+  participant R as Remote
+  C->>S: req file with CID and hint
+  Note over C,S: The (optional) hint is a room+event ID
+  activate S
+  opt fetch file from remote
+    loop try potential remotes
+      S->>R: req file
+      activate R
+      R-->>S: serve file
+      deactivate R
+    end
+  end
+  S->>S: verify the CID
+  S-->>C: serve file
+  deactivate S
+  opt verify CID
+    C->>C: verify the CID
+  end

proposals/images/2846-sending-current.mermaid

@@ -0,0 +1,7 @@
+sequenceDiagram
+  participant C as Client
+  participant S as Server
+  C->>S: upload file
+  S-->>C: return MXC URL
+  C->>S: send event with MXC URL
+  S-->>C: return event ID

proposals/images/2846-sending-proposed.mermaid

@@ -0,0 +1,17 @@
+sequenceDiagram
+    participant C as Client
+    participant S as Server
+    C->>S: upload file
+    activate S
+    S->>S: calculate CID
+    S-->>C: return MXC URL with CID
+    deactivate S
+
+    opt verify CID
+      C->>C: verify the CID
+    end
+
+    C->>S: send event with MXC URL
+    activate S
+    S-->>C: event ID
+    deactivate S