[@realm/tools] Set up the package. Initial import of realm-schema. (r…

…ealm#4538)

* [@realm/tools] Set up the package. 
* Initial import of realm-schema.

Co-authored-by: Kræn Hansen <[email protected]>

packages/realm-tools/.eslintignore

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+/dist/

packages/realm-tools/.eslintrc.json

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+{
+ "parser": "@typescript-eslint/parser",
+ "extends": [
+ "plugin:@typescript-eslint/recommended"
+ ],
+ "rules": {
+ "@typescript-eslint/explicit-function-return-type": "off"
+ }
+}

packages/realm-tools/.gitignore

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+dist/

packages/realm-tools/CHANGELOG.md

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+x.x.x Release notes (yyyy-MM-dd)
+=============================================================
+### Breaking changes
+* None
+
+### Enhancement
+* Added the tool `realm-schema` to inspect the schema in a Realm file.
+
+### Fixes
+* None
+
+### Internal
+* None

packages/realm-tools/LICENSE

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+../../LICENSE

packages/realm-tools/README.md

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+# Tools for Realm
+
+## Introduction
+
+This package contains various tools for working with Realm files. Each tool is briefly documented here.
+
+## Installation
+
+The prerequisite for installing the `@realm/tools` package is a working [node.js](https://nodejs.org/en/) and a package manager.
+
+npm:
+
+```sh
+npm install -g @realm/tools
+```
+
+yarn:
+
+```sh
+yarn global add @realm/tools
+```
+
+## Building
+
+Source code for all tools are found in `src`. The output of the build process is found in `dist`.
+
+```sh
+npm install
+npm run build
+```
+
+You can run the transpiled tools directly e.g.,
+
+```sh
+node dist/realm-schema.js -h
+```
+
+## `realm-schema`
+
+The `realm-schema` can read a local Realm file and export the schema. The support output formats are:
+
+* JSON
+* [Mermaid](https://mermaid-js.github.io/mermaid/#/) compatible class diagram
+
+Example:
+
+```sh
+npx realm-schema -i samples/default.realm -o MyClasses.mmd -f mermaid
+```
+
+The output will look like
+
+```mermaid
+classDiagram
+class Child {
+ +string name
+ +int age
+}
+class Parent {
+ +string name
+ +string city
+ +Parent marriedTo
+ +list~Child~ children
+}
+Parent <-- Parent
+Child <-- Parent
+```
+If you plan to use the JSON output, it is recommended to use it with [jq](https://stedolan.github.io/jq/).