Add LSKx89 dual matched JFETs

Add LSK389, LSK489 and LSK589 dual matched low-noise JFETs.

Footprint MR for TO71 package: kicad-footprints!3257.

KLC violations:

• Violating S4.1 - https://klc.kicad.org/symbol/s4/s4.1/ General pin requirements
• Violating S3.1 - https://klc.kicad.org/symbol/s3/s3.1/ Origin is centered on the middle of the symbol
  JFET symbol with violations are copied from Device library
• Violating S5.1 - https://klc.kicad.org/symbol/s5/s5.1/ Symbols with a default footprint link to a valid footprint file
  See footprint MR above.

Parts

• LSK389
  • LSK389_TO71
  • LSK389_SOIC
• LSK489
  • LSK489_TO71 (derived from LSK389_TO71)
  • LSK489_SOIC (derived from LSK389_SOIC)
  • LSK489_SOT23
• LSK589
  • LSK589_TO71 (derived from LSK389_TO71)
  • LSK589_SOIC (derived from LSK389_SOIC)
  • LSK589_SOT23 (derived from LSK489_SOT23)

Datasheets:

• LSK389: https://www.linearsystems.com/_files/ugd/7e8069_e8cb0edf8dc64ae79ae575c7a40c2828.pdf
• LSK489: https://www.linearsystems.com/_files/ugd/7e8069_0e97881584d2424baa3f3ad67a624446.pdf
• LSK589: https://www.linearsystems.com/_files/ugd/7e8069_c146edec36c54f129db7eba3251427fa.pdf

Screenshots:

Part A and B

Part C (LSKx89_SOIC only)

• Remove the instructional content of this template
• Provide a URL to a datasheet for the symbol(s) you are contributing
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.