Update immer dependency for website to fix dependabot alert

[alangpierce]

CRA is still in the process of updating with the immer fix
( facebook/create-react-app#10412 ), so this uses a
resolution override to use the newest immer. To reduce chance of compatibility
issues, I also updated react-dev-utils to latest and confirmed that dev and
prod builds both still work.

[codecov]

Codecov Report

Merging #595 (228189a) into main (a1d5776) will decrease coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #595      +/-   ##
==========================================
- Coverage   81.95%   81.87%   -0.09%     
==========================================
  Files          55       55              
  Lines        5808     5571     -237     
  Branches     1314     1314              
==========================================
- Hits         4760     4561     -199     
+ Misses        764      726      -38     
  Partials      284      284              

Impacted Files	Coverage Δ
src/Options-gen-types.ts	75.00% <0.00%> (-25.00%)	⬇️
src/parser/index.ts	77.77% <0.00%> (-7.94%)	⬇️
src/computeSourceMap.ts	83.33% <0.00%> (-5.56%)	⬇️
src/util/getNonTypeIdentifiers.ts	94.44% <0.00%> (-5.56%)	⬇️
src/parser/plugins/types.ts	91.66% <0.00%> (-3.34%)	⬇️
src/parser/tokenizer/readWord.ts	82.35% <0.00%> (-3.02%)	⬇️
src/parser/traverser/util.ts	86.20% <0.00%> (-2.17%)	⬇️
src/parser/traverser/base.ts	95.45% <0.00%> (-1.69%)	⬇️
src/parser/traverser/statement.ts	82.18% <0.00%> (-0.44%)	⬇️
src/parser/traverser/lval.ts	98.59% <0.00%> (-0.26%)	⬇️
... and 19 more

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[github-actions]

Benchmark results

Before this PR: 322.8 thousand lines per second
After this PR: 322.2 thousand lines per second

Measured change: 0.19% slower (2.81% slower to 0.91% faster)
Summary: Likely no significant difference