Add common ASIC/FPGA file formats to GitHub/linguist

# Brief explanation

GitHub uses https://github.com/github/linguist to do language stats. Currently the https://github.com/github/linguist/blob/master/lib/linguist/languages.yml file is missing a lot of important file formats used in FPGA/ASIC development.

Of the top of my head;
- [ ] `.gds`
- [ ] `.lib` - Liberty timing files
- [ ] `.oa` - OpenAccess files
- [ ] `.spice` - Spice simulation files
- [ ] `mag`, `maglef` - magic
- [ ] `LEF`
- [ ] `CDL`

Commercial file formats;
- [ ] Cadence file format names
- [ ] Calibre file format names

Should check the following are covered too.
* `* .v` - Verilog (C like -- should use a // comments, supports /* */ too)
* `* .vh` - Verilog header (C like -- should use a // comments, supports /* */ too)
* `* .sv` - SystemVerilog (should use /* */ comments, supports /* */ too)
* `* .svh` - SystemVerilog header (should use /* */ comments, supports /* */ too)
* `* .tcl` - TCL (should use # comments)
* `* .sdc` / `*.xdc` - Synopsis Design Constraint / Xilinx Design Constraint files -- Really TCL scripts (see above)
* `.blif`/`.eblif` - Berkley Logic Interface Format (uses bash # style comments)
* `.edif` - Electronic Design Interchange Format (S-Expressions based -- unknown comment style?)
* `.lef` - Library Exchange Format (should use # comments)
* `.lib` - Liberty Timing File (should use /* */ style comments)
* `.sdf` - Standard Delay Format (LISP file which supports /* */ and // comments)
* `.spef` - Standard parasitics exchange format (supports only // style comments)