message: chore: update readme to reflect new clades and algorithm changes
diff: @@ -29,12 +29,13 @@ Since its emergence in late 2019, SARS-CoV-2 has diversified into several differ
  facilitate discussion of these variants, we have grouped them into __clades__ which are defined by specific
  signature mutations.
  -We currently define 5 major clades (see [this blog post](https://nextstrain.org/blog/2020-06-02-SARSCoV2-clade-naming)
  +We currently define 11 major clades (see [this blog post](https://nextstrain.org/blog/2021-01-06-updated-SARS-CoV-2-clade-naming)
  for details):
  - 19A and 19B emerged in Wuhan and have been dominating the early outbreak
  - 20A emerged from 19A out of dominated the European outbreak in March and has since spread globally
  -- 20B and 20C are large genetically distinct subclades 20A
  +- 20B and 20C are large genetically distinct subclades 20A emerged in early 2020
  +- 20D to 20I have emerged over the summer of 2020 and include two "variants of concern" (VOC) with signature mutations S:N501Y.
  <figure className="figure w-100 text-center">
  <picture className="w-75 figure-img" alt="illustration of the model">
  @@ -47,7 +48,7 @@ for details):
  Within Nextstrain, we define each clade by its combination of signature mutations.
  You can find the exact clade definition in [github.com/nextstrain/ncov](https://github.com/nextstrain/ncov/blob/master/defaults/clades.tsv).
  -Nextclade assigns your sequences to these clades by checking them for these mutations.
  +Nextclade assigns your sequences to these clades by placing them on a phylogenetic tree annotated with these clade definitions.
  ### Quality Control (QC)
  @@ -81,7 +82,7 @@ These include for example: primer sequences, adaptaters, or chimeras between div
  ## How does it work?
  At the core of Nextclade is a pairwise sequence alignment between the reference sequence and each of the sequences in your data.
  -Once the sequences are aligned, we can identify differences between them and use these differences to assign clades and identify quality issues.
  +Once the sequences are aligned, we can identify differences between them and use these differences to place the sequence on the phylogeny and identify quality issues.
  ### Sequence Alignment
  @@ -92,7 +93,7 @@ For Nextclade, we therefore implemented a banded-pairwise alignment algorithm in
  We roughly estimate the alignment of your sequences to the reference one-by-one using short seeds (21-mers) along the sequence.
  With this rough overall alignment, we perform a [banded Smith-Waterman alignment](https://github.com/nextstrain/nextclade/blob/master/packages/web/src/algorithms/alignPairwise.ts) with an affine gap-penalty.
  -If the seed matches are poor or suggest gaps in excess of 200 bases, we won't attempt to align -- your sequence won't be
  +If the seed matches are poor or suggest gaps in excess of 400 bases, we won't attempt to align -- your sequence won't be
  scored.
  Large gaps require a lot of memory and computation in our current implementation.
  For most sequences, however, this alignment strategy works well and takes less than a second per sequence.
  