docs: English translation updates (#190)

* docs: Add CLI article (en)

* docs: Update frames article (en)

* docs: Add article about part models (en)

* docs: Update Raspberry Pi article (en)

* docs: Remove unused raspberry3.jpg

* docs: Add COEX Pix article (en)

* docs: Add CopterHack 2019 article (en)

* docs: Update connection article (en)

* docs: Add programming overview (en)

* docs: Add anchor in modes article

* docs: Fix link in auto_setup, add editing ID (en)

* docs: Rearrange summary to match Russian version (en)

* docs/camera_frame: Add link to cli#editing (en)

* docs/wifi: Fix link to next article (en)

* docs: Add "next" links where appropriate (en)

docs/en/cli.md

@@ -0,0 +1,80 @@
+# Command line interface
+
+The Raspberry Pi OS, Raspbian, uses CLI as its primary user interface (which is common for Linux-based operating systems). You can use [a secure shell connection](ssh.md) to access the command line.
+
+## Basic commands
+
+> **Hint** Double-tapping the `Tab ↹` key autocompletes the command or its argument. This is known as "tab completion".
+
+Show the contents of the current directory:
+
+```bash
+ls
+```
+
+Change current (working) directory:
+
+```bash
+cd catkin_ws/src/clever/clever/launch
+```
+
+Go one directory level up:
+
+```bash
+cd ..
+```
+
+Print path to the current directory:
+
+```bash
+pwd
+```
+
+Print contents of the `file.py` file:
+
+```bash
+cat file.py
+```
+
+Run `file.py` as a Python script:
+
+```bash
+python file.py
+```
+
+Reboot Raspberry Pi:
+
+```bash
+sudo reboot
+```
+
+You can terminate currently running (foreground) program by pressing `Ctrl`+`C`.
+
+Read more about the Linux command line in the Raspberry Pi documentation: https://www.raspberrypi.org/documentation/linux/usage/commands.md.
+
+## Editing files {#editing}
+
+You can use **nano** to edit files on the Raspberry Pi. It is one of the more user-friendly console-based text editor.
+
+1. Use the following command to edit or create a file:
+
+   ```bash
+   nano path/to/file
+   ```
+
+   For example:
+
+   ```bash
+   nano ~/catkin_ws/src/clever/clever/launch/clever.launch
+   ```
+
+   <img src="../assets/nano.png" alt="Editing files in nano" data-action="zoom">
+2. Edit the file.
+3. Press `Ctrl`+`X`, `Y`, `Enter` to save your file and exit.
+4. Restart the `clever` package if you've changed .launch files:
+
+   ```bash
+   sudo systemctl restart clever
+   ```
+
+You may also use other editors like **vim** if you prefer.