Add pkg SOT89-3

[ubruhin]

SUMMARY

Adding SOT89-3 from the JEDEC TO-243 standard. Package is manually created, STEP model generated by LibrePCB/librepcb-parts-generator#151. Added a separate footprint variant for hand-soldering.

DATASHEETS / REFERENCES

• TO-243C: https://www.jedec.org/standards-documents/docs/243-c
• https://www.nxp.com/docs/en/package-information/SOT89.pdf
• https://www.diodes.com/assets/Package-Files/SOT89.pdf
• https://ww1.microchip.com/downloads/en/DeviceDoc/MCP1700-Data-Sheet-20001826F.pdf

OPEN QUESTIONS / UNRESOLVED ISSUES

• I could not find out what would be the IPC7351C naming for this package. Therefore it is named "SOT89-3" for now, as usually named in datasheets.
• The lead lengths (how far they go under the body) is not standardized in JEDEC and is often not even documented in datasheets. Also the recommended footprints vary quite heavily. I tried to find some reasonable footprint geometry as a mix of the datasheets I have found.
• Since pad 2 is very large, I manually added a smaller solder paste mask similar to what NXP recommends.

CHECKLIST

• I have read and followed the library conventions¹.
• For packages, I followed IPC7351C (see details in library conventions).
• For modified elements, I bumped their version number².
• I already used the new library elements in a design and verified their correctness (optional).
• I'm the copyright owner of the added content (i.e. the changes are made by myself, not copied/imported from somewhere else).
• I agree to publish all my changes under the CC0 Public Domain License³, allowing everyone to use and modify the content without any restrictions.

¹ Library Conventions: https://docs.librepcb.org/#libraryconventions
² Minor version bump if only metadata was modified (e.g. "0.1" -> "0.1.1"), major version bump if functional changes were made (e.g. "0.1" -> "0.2")
³ CC0 Public Domain License: https://en.wikipedia.org/wiki/CC0