feat: support graphql subscriptions

[Diizzayy]

This PR adds support for GraphQL subscriptions.

Can be tested by installing the latest edge version via yarn add -D nuxt-graphql-client@edge

[codecov]

Codecov Report

Merging #239 (a8bfa42) into main (453aac0) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head a8bfa42 differs from pull request most recent head d0a5d85. Consider uploading reports for the commit d0a5d85 to get more accurate results

@@            Coverage Diff             @@
##             main     #239      +/-   ##
==========================================
- Coverage   93.70%   93.66%   -0.05%     
==========================================
  Files           6        7       +1     
  Lines         620      600      -20     
  Branches      122      124       +2     
==========================================
- Hits          581      562      -19     
+ Misses         39       38       -1     

Impacted Files	Coverage Δ
src/generate.ts	94.80% <ø> (-0.07%)	⬇️
examples/subscription/nuxt.config.ts	100.00% <100.00%> (ø)
src/context.ts	99.13% <100.00%> (+0.65%)	⬆️
src/module.ts	89.75% <100.00%> (-0.16%)	⬇️
examples/multi-client/nuxt.config.ts	100.00% <0.00%> (ø)

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[darvids0n]

Hi there! I'm looking for a nuxt3 module for gql

I just noticed Diizzayy/ogql@9f2cf65

Do you have a rough idea of when this will make it here? I'm choosing between @nuxtjs/apollo and nuxt-graphql-client for a platform and it seems you currently maintain both.

I'm also keen to check which has better offline support (i.e. network down but I want to fetch the output of previous queries if they are cached).

[Clex1o1]

Still something open on this one? Maybe we can help?