docs: Update _index.md

[dorbin]

Just adding "2.0" to title on /docs/ landing page. This is to make it clearer, for users coming in from Google Cloud Deploy docs, that they're looking at the 2.0 docs, distinct from the docs on skaffold.dev.

Fixes: #nnn
Related: Relevant tracking issues, for context
Merge before/after: Dependent or prerequisite PRs

Description

User facing changes (remove if N/A)

Follow-up Work (remove if N/A)

[codecov]

Codecov Report

Merging #7951 (e1e24d2) into main (290280e) will decrease coverage by 3.62%.
The diff coverage is 53.94%.

@@            Coverage Diff             @@
##             main    #7951      +/-   ##
==========================================
- Coverage   70.48%   66.86%   -3.63%     
==========================================
  Files         515      594      +79     
  Lines       23150    28768    +5618     
==========================================
+ Hits        16317    19235    +2918     
- Misses       5776     8121    +2345     
- Partials     1057     1412     +355     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/test.go	44.44% <0.00%> (ø)
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/render.go	35.48% <18.18%> (-5.90%)	⬇️
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/run.go	64.28% <33.33%> (-9.63%)	⬇️
cmd/skaffold/app/cmd/fix.go	56.41% <37.50%> (-20.07%)	⬇️
cmd/skaffold/app/cmd/verify.go	41.17% <41.17%> (ø)
... and 368 more

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[aaron-prindle]

LGTM!