Move docs/ to docs/en/

It allows comparison between the directories and helps translations.

docs/en/flashing.md

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+# Flashing Instructions
+
+In general, we recommend using the instructions in `README.md`, however, mostly
+as a development artifact, another method of flashing KMK exists (tested and
+supported only on Linux, though it should also work on macOS, the BSDs, and
+other Unix-likes. It may also work on Cygwin and the Windows Subsystem for
+Linux).
+
+Given `make` and `rsync` are available on your system (in `$PATH`), the
+following will copy the `kmk` tree to your CircuitPython device, and will copy
+the file defined as `USER_KEYMAP` as your `main.py`. It will also copy our
+`boot.py`, which allocates a larger stack size (simply - more of the device's
+RAM will be available to KMK and your keyboard config) than CircuitPython's
+default. If any of these files exist on your CircuitPython device already, they
+will be overwritten without a prompt.
+
+If you get permissions errors here, **don't run make as root or with sudo**. See
+`Troubleshooting` below.
+
+```sh
+make MOUNTPOINT=/media/CIRCUITPY USER_KEYMAP=user_keymaps/nameofyourkeymap.py BOARD=board/nameofyourboard/kb.py
+```
+
+# Troubleshooting
+## Linux/BSD
+
+Check to see if your drive may have mounted elsewhere with a GUI tool or other
+automounter. Most of these tools will mount your device under `/media`, probably
+as `/media/CIRCUITPY`.  If it's not mounted, you can read up on how to mount a
+drive manually
+[here](https://wiki.archlinux.org/index.php/File_systems#Mount_a_file_system).
+
+For example,
+
+`sudo mount -o uid=$(id -u),gid=$(id -g) /dev/disk/by-label/CIRCUITPY ~/mnt`
+
+If you're still having issues, check out our support page to see where you can
+come say hi and the community will gladly help you out.