Update README for new jumpers, and add section on headers With the new jumpers adding headers is possible, so that the Teensy is removable without desoldering

Add more jumpers for Teensy++ 2.0 compat This avoids requiring folks to pull pins out of headers for Teensy++ 2.0 compatibility, instead just requiring them to cut the traces, which I think is better and more importantly is reversible, so that if someone builds with a Teensy++ 2.0 and then wants to replace it with a 3.6, they can just re-close the new jumpers, desolder the old ones, and be good to go.

README: add section about installation

README: fix image source branch name

Update to the new project file format (#47) I opened and saved the project and its schematic, PCB, etc. Some got saved with a different file name extension. `kinx-cache.lib` had to been renamed to `kint-cache.lib` otherwise the Schematic editor would complain that the file is missing. Then I removed it as I was told in the IRC channel that after saving the schematic in the new format, the symbols will be embedded and it's no longer needed. When opening the PCB there was a warning: > If the zones on this board are refilled the Copper Edge Clearance > setting will be used (see Board Setup > Design Rules > Constraints). > This may result in different fills from previous KiCad versions which > used the line thicknesses of the board boundary on the Edge Cuts > layer. The File > Board Setup > Design Rules > Constraints > Copper Edge Clearance is 0.05mm. Clicking the board boundary belonging to the Edge Cuts layer reveals a properties dialog with Line Width 0.05mm. Being the same, nothing should change at the next refill. The `.gitignore` file has been updated from its original source.

Update README.md (#44) https://forum.kicad.info/t/warning-avoid-all-links-to-kicad-pcb-org-use-kicad-org/31521

README: link to kint41 QMK configurator

README: made for Teensy 3.x and 4.x

README: recommend Teensy 4.1, then Teensy 3.6

README: no longer recommend the Teensy++ 2.0