maintenance: update pnpm version

[MH4GF]

Problem

Currently, when dependabot runs CI, the following error occurs:

Run pnpm install --frozen-lockfile
 WARN  Ignoring not compatible lockfile at /home/runner/work/graphql-codegen-typescript-validation-schema/graphql-codegen-typescript-validation-schema/pnpm-lock.yaml
 ERR_PNPM_NO_LOCKFILE  Cannot install with "frozen-lockfile" because pnpm-lock.yaml is absent

Note that in CI environments this setting is true by default. If you still need to run install in such cases, use "pnpm install --no-frozen-lockfile"
Error: Process completed with exit code 1.

ref: https://github.com/Code-Hex/graphql-codegen-typescript-validation-schema/actions/runs/9271635994/job/25507513605

pnpm-lock.yaml seems to be incompatible, but that was because the version of pnpm running in CI is older.

Solution

• Bump up the pnpm version to v9.
• Manage the pnpm version in package.json
  • pnpm is available with corepack enable.
  • You can also update the pnpm version with dependabot if you do it this way.
• Refer to it in CI.

[Code-Hex]

@MH4GF Thanks! I fix this in another PR 🙏