Add file transfer instructions to README

Enhanced the README with clear examples for uploading and downloading files, and for interaction with pastes via curl or browser. This update should assist users in performing common tasks without needing to refer to external documentation, improving ease of use.

README.md

@@ -38,6 +38,12 @@ With the exception of the `-u` option, all arguments of the original Fiche
 should work as expected. `-u` is not implemented because, well, just use the
 right user in the first place. 🤷‍♀️
 
+#### Uploading files
+
+```bash
+$ nc <server> <port> < <file>
+```
+
 ### Recup Server
 
 ```bash
@@ -45,6 +51,14 @@ $ source venv/bin/activate
 $ pyfiche-recup # try --help for options
 ```
 
+#### Downloading files
+
+Pipe the ID of an uploaded file to `nc`:
+
+```bash
+$ echo <id> | nc <server> <port> > <file>
+```
+
 ### Lines Server
 
 ```bash
@@ -52,6 +66,28 @@ $ source venv/bin/activate
 $ pyfiche-lines # try --help for options
 ```
 
+#### Viewing pastes in a browser
+
+Go to `http://<server>:<port>/<id>`.
+
+#### Downloading raw pastes
+
+```bash
+$ curl http://<server>:<port>/<id>/raw
+```
+
+#### Uploading pastes
+
+```bash
+$ curl -X POST -d '<paste content>' http://<server>:<port>
+```
+
+Or use a file:
+
+```bash
+$ curl -X POST -d @<file> http://<server>:<port>
+```
+
 ## License
 
 PyFiche is licensed under the MIT license. See the [LICENSE](LICENSE) file for