26 router manuals added

Links to 26 more router and modem manuals were added:

- Cisco: 4 user guides, 5 quick start guides, 2 installation guides, 1 hardware manual
- Huawei: 3 user guides
- Linksys: 1 user guide, 1 configuration guide, 1 quick installation guide
- Netgear: 2 user manuals, 2 quick start guides, 4 reference manuals