Add links for technology examples

PORTING.md

@@ -6,19 +6,24 @@ If you want to support a new technology, you will need to create:
 
 We provide two technology examples for [SCMOS] and [FreePDK45]. Each
 specific technology (e.g., [FreePDK45]) should be a subdirectory
-(e.g., $OPENRAM_TECH/freepdk45) and include certain folders and files:
-* gds_lib folder with all the .gds (premade) library cells:
-  * dff.gds
-  * sense_amp.gds
-  * write_driver.gds
-  * cell_1rw.gds
-  * replica\_cell\_1rw.gds
-  * dummy\_cell\_1rw.gds
-* sp_lib folder with all the .sp (premade) library netlists for the above cells.
-* layers.map
-* A valid tech Python module (tech directory with \_\_init\_\_.py and tech.py) with:
+(e.g., `$OPENRAM_TECH/freepdk45`) and include certain folders and files:
+* `gds_lib` folder with all the `.gds` (premade) library cells:
+  * `dff.gds`
+  * `sense_amp.gds`
+  * `write_driver.gds`
+  * `cell_1rw.gds`
+  * `replica\_cell\_1rw.gds`
+  * `dummy\_cell\_1rw.gds`
+* `sp_lib` folder with all the `.sp` (premade) library netlists for the above cells.
+* `layers.map`
+* A valid tech Python module (tech directory with `__init__.py` and `tech.py`) with:
   * References in tech.py to spice models
   * DRC/LVS rules needed for dynamic cells and routing
   * Layer information
   * Spice and supply information
   * etc.
+
+
+
+[FreePDK45]: https://www.eda.ncsu.edu/wiki/FreePDK45:Contents
+[SCMOS]:     https://www.mosis.com/files/scmos/scmos.pdf