refactor: Migrate project from Deno to pnpm/Node

Replace Deno configs and workflows with pnpm/Node tooling Add
package.json, jsr.json, build.config.ts and pnpm-lock.yaml Remove
deno.json, deno.lock, Deno build scripts and workflow Move source files
into src/ and update imports and tests to vitest Add Test CI workflow
and adapt publish jobs for pnpm/node Update editor settings, tasks,
.gitignore and bump LICENSE year

jsr.json

@@ -0,0 +1,6 @@
+{
+  "name": "@textplace/core",
+  "version": "0.5.0",
+  "exports": "./src/mod.ts",
+  "include": ["src/**/*.ts", "LICENSE", "README.md"]
+}