Install typia

GitGitGadget now accepts the project configuration as a `config` Action
input, in the form of a string that contains the JSON-encoded `IConfig`
object. That is a bit fragile, though, as it is all-too-easy to have a
typo in that object.

Let's install `typia` to use the `IConfig` interface as a source of
truth when validating the user input.

In a slight variation of what is recommended at https://typia.io/docs/
setup/, I ran:

  npm install --save-dev typia
  npx typia setup

Then, I undid the damage done to `tsconfig.json` ;-) (`npx typia setup`
edited that file and wanted to add just a plugin, but changed plenty of
white-space, getting utterly confused by the commented-out lines.)

Finally, to fix running the tests via `ts-jest`, I needed to force
it to use `ts-patch`, which unfortunately runs into problems because
of 281204b (fix: set isolatedModules true for ts-jest, 2025-11-05),
because the `ts-patch` transformation is only triggered with
`isolatedModules: false`:

  "compiler": "ts-patch/compiler",
  "tsconfig": {
    "isolatedModules": false
  },

Sadly, this spits out the warning "ts-jest[config] (WARN) message
TS151002: Using hybrid module kind (Node16/18/Next) is only
supported in "isolatedModules: true". Please set "isolatedModules:
true" in your tsconfig.json. To disable this message, you can set
"diagnostics.ignoreCodes" to include 151002 in your ts-jest config.
See more at https://kulshekhar.github.io/ts-jest/docs/getting-started/
options/diagnostics". We abide by that suggestion:

  "diagnostics": {
    "ignoreCodes": [151002]
  },

Note that `npx typia setup` also switched the version coupling from

  "typescript": "^5.9.3"

to

  "typescript": "~5.9.3"

but we do not want that, so I undid that change in `package.json` and
`package-lock.json` manually.

Assisted-by: Claude Opus 4.6
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho