Release 0.6.4

This is release 0.6.4 of covid-spike-classification.

This release adds the following mutations:

• L452M as found in various BA.1/BA.2 subtypes
• F486V as found in BA.4/BA.5
• Q677E as found in BA.2.3.1
• S704L as found in BA.1.9

Detailed changes:

Kai Blin (5):
      core: Add F486V mutation call
      core: Add L452M mutation call
      core: Add S704L mutation call
      core: Add Q677E mutation call
      Bump version to 0.6.4