docs(parser): create packages/parser README.md file

packages/parser/README.md

@@ -0,0 +1,63 @@
+<p align="center">
+<img src="https://raw.githubusercontent.com/mermaid-js/mermaid/develop/docs/public/favicon.svg" height="150">
+
+</p>
+<h1 align="center">
+Mermaid Parser
+</h1>
+
+<p align="center">
+Mermaid parser package
+<p>
+
+[![NPM](https://img.shields.io/npm/v/mermaid-parser)](https://www.npmjs.com/package/mermaid-parser)
+
+## How the package works
+
+The package exports a `parse` function that has two parameters:
+
+```ts
+declare function parse<T extends DiagramAST>(
+  diagramType: keyof typeof initializers,
+  text: string
+): T;
+```
+
+## How does a Langium-based parser work?
+
+```mermaid
+sequenceDiagram
+actor Package
+participant Module
+participant TokenBuilder
+participant Lexer
+participant Parser
+participant ValueConverter
+
+
+Package ->> Module: Create services
+Module ->> TokenBuilder: Override or/and<br>reorder rules
+TokenBuilder ->> Lexer: Read the string and transform<br>it into a token stream
+Lexer ->> Parser: Parse token<br>stream into AST
+Parser ->> ValueConverter: Clean/modify tokenized<br>rules returned value
+ValueConverter -->> Package: Return AST
+```
+
+- When to override `TokenBuilder`?
+
+  - To override keyword rules.
+  - To override terminal rules that need a custom function.
+  - To manually reorder the list of rules.
+
+- When to override `Lexer`?
+
+  - To modify input before tokenizing.
+  - To insert/modify tokens that cannot or have not been parsed.
+
+- When to override `LangiumParser`?
+
+  - To insert or modify attributes that can't be parsed.
+
+- When to override `ValueConverter`?
+
+  - To modify the returned value from the parser.

packages/parser/package.json

@@ -7,7 +7,7 @@
     "Yokozuna59",
     "Sidharth Vinod (https://sidharth.dev)"
   ],
-  "homepage": "https://github.com/mermaid-js/mermaid/#readme",
+  "homepage": "https://github.com/mermaid-js/mermaid/tree/develop/packages/mermaid/parser/#readme",
   "types": "dist/src/index.d.ts",
   "type": "module",
   "exports": {