Create router.3ds.md (#1523)

* Create router.3ds.md

Create a `.router` command equivalent for the 3DS, using the Wii counterpart as a template and https://discord.com/channels/196618637950451712/196635695958196224/1507491489414905968 as a source of information

* Update router.3ds.md

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Co-authored-by: eip <36315290+eip618@users.noreply.github.com>

cogs/assistance-cmds/router.3ds.md

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+---
+title: Common problems when connecting your 3DS to your router
+help-desc: Some troubleshooting steps to connect your 3DS to the Internet
+---
+
+- The 3DS needs a 2.4GHz wifi network, not 5GHz.
+- Your device and 3DS must be on the same network, on the same band and channel. Mesh networks (Google Home, etc) can _sometimes_ interfere with this.
+- The network must have at most WPA2-PSK security - anything on WPA3 won't work.
+
+Advanced tech settings:
+- 802.11b/g/n enabled
+- WPA2-PSK/Personal (AES / CPMM-128 only)
+- The channel must be set to 1, 6 or 11
+- width of 20MHz
+- must not be restricted to AX-only
+- if possible, set PMF (802.11w) to Optional
+
+Known routers incompatible with these settings:
+- Xfinity
+- Spectrum
+
+If your ISP will not let you change these settings, you have a few options:
+- You can try a hotspot. This is not recommended, as it usually results in an unstable connection.
+- Alternatively, you can buy a cheap router and use the ISP you already have, like a mesh network.