ci: init markdown-lint and resolve linter issues (#50)

Closes: WORLD-983

## Overview

Add markdown linter

## Brief Changelog

- https://github.com/marketplace/actions/markdown-lint
- fix markdown linter issues
- customize markdown linter config:
  - increase `MD013/line-length` default line length from 80 (too short), to 250 (median "looks good" line length in our docs)
  - add `MD033/no-inline-html` necessary allowed HTML element

## Testing and Verifying

- CI passed
- Lint error annotation detected on changed code:
![image](https://github.com/Argus-Labs/world-engine/assets/29672212/01907dea-6de6-413e-aac8-d92e9734c00b)
![image](https://github.com/Argus-Labs/world-engine/assets/29672212/3664194a-5ee8-4e68-be79-c6784a63501f)

.github/workflows/lint-md.yml

@@ -0,0 +1,27 @@
+name: Lint
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+    paths:
+      - "**.md"
+  push:
+    branches:
+      - main
+    paths:
+      - "**.md"
+
+jobs:
+  lint-md:
+    name: Markdown
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      ## detect errors from markdownlint-cli and create annotations for them
+      - uses: xt0rted/markdownlint-problem-matcher@v3
+      - uses: articulate/actions-markdownlint@v1
+        with:
+          config: .markdownlint.yaml
+          ignore: vendor
+          version: 0.39.0

.markdownlint.yaml

@@ -0,0 +1,21 @@
+---
+# Default state for all rules
+default: true
+
+# MD013/line-length : Line length : https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md013.md
+MD013:
+  ## Increase line length from default '80'
+  line_length: 250
+  ## exluce code_blocks from line linter
+  code_blocks: false
+
+# MD033/no-inline-html : Inline HTML : https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md033.md
+MD033:
+  allowed_elements:
+  - img
+  - div
+  - br
+  - a
+  - pre
+  - h1
+  - p

README.md

@@ -1,4 +1,4 @@
-<div align="center">
+<div align="center"> <!-- markdownlint-disable-line first-line-heading -->
 <img alt="World CLI Logo" src="https://i.imgur.com/XM74ODi.png" width="378">
 <p>A swiss army knife for creating, managing, and deploying World Engine projects</p>
   <p>
@@ -35,13 +35,15 @@ World CLI has been rigorously tested on macOS and Linux.
 If you are using Windows, you will need
 [WSL](https://docs.microsoft.com/en-us/windows/wsl/install-win10) to install and use the CLI.
 
-**Install latest release**
-```
+**Install latest release:**
+
+```shell
 curl https://install.world.dev/cli! | bash
 ```
 
-**Install a specific release**
-```
+**Install a specific release:**
+
+```shell
 curl https://install.world.dev/cli@<release_tag>! | bash
 ```
 
@@ -53,17 +55,17 @@ This section is for devel developers who want to contribute to the World CLI.
 If you want to develop a World Engine project using World CLI, see the
 [World Engine quickstart guide](https://world.dev/quickstart)
 
-**Building from source**
+**Building from source:**
 
-```
+```shell
 make build
 ```
 
-**Testing your local build**
+**Testing your local build:**
 
 You can test your local build of World CLI by running the following command.
 This will install the World CLI binary in your `/usr/local/bin` directory.
 
-```
+```shell
 make install
-```
+```