docs: use @alpha for installing packages (#121)

## Description

Update the docs to install our packages with the `@alpha` channel
because we are currently in pre-release / alpha mode so trying to just
install `sit-onyx` would always install version `0.0.0` although we
already have e.g. version `1.0.0-alpha.1`

apps/docs/src/getting-started.md

@@ -22,15 +22,15 @@ Install the npm package with your corresponding package manager:
 ::: code-group
 
 ```sh [pnpm]
-pnpm add sit-onyx
+pnpm add sit-onyx@alpha
 ```
 
 ```sh [npm]
-npm install sit-onyx
+npm install sit-onyx@alpha
 ```
 
 ```sh [yarn]
-yarn install sit-onyx
+yarn install sit-onyx@alpha
 ```
 
 :::

apps/docs/src/packages/figma-utils.md

@@ -21,7 +21,7 @@ import packageJson from "../../../../packages/figma-utils/package.json";
 For a list of supported commands and options, run:
 
 ```sh
-npx @sit-onyx/figma-utils@latest --help
+npx @sit-onyx/figma-utils@alpha --help
 ```
 
 ::: tip Usage in CI
@@ -44,15 +44,15 @@ Install the npm package with your corresponding package manager:
 ::: code-group
 
 ```sh [pnpm]
-pnpm add @sit-onyx/figma-utils
+pnpm add @sit-onyx/figma-utils@alpha
 ```
 
 ```sh [npm]
-npm install @sit-onyx/figma-utils
+npm install @sit-onyx/figma-utils@alpha
 ```
 
 ```sh [yarn]
-yarn install @sit-onyx/figma-utils
+yarn install @sit-onyx/figma-utils@alpha
 ```
 
 :::

apps/docs/src/packages/headless.md

@@ -34,15 +34,15 @@ Install the npm package with your corresponding package manager:
 ::: code-group
 
 ```sh [pnpm]
-pnpm add @sit-onyx/headless
+pnpm add @sit-onyx/headless@alpha
 ```
 
 ```sh [npm]
-npm install @sit-onyx/headless
+npm install @sit-onyx/headless@alpha
 ```
 
 ```sh [yarn]
-yarn install @sit-onyx/headless
+yarn install @sit-onyx/headless@alpha
 ```
 
 :::

apps/docs/src/packages/storybook-utils.md

@@ -28,15 +28,15 @@ Install the npm package with your corresponding package manager:
 ::: code-group
 
 ```sh [pnpm]
-pnpm add -D @sit-onyx/storybook-utils
+pnpm add -D @sit-onyx/storybook-utils@alpha
 ```
 
 ```sh [npm]
-npm install -D @sit-onyx/storybook-utils
+npm install -D @sit-onyx/storybook-utils@alpha
 ```
 
 ```sh [yarn]
-yarn install -D @sit-onyx/storybook-utils
+yarn install -D @sit-onyx/storybook-utils@alpha
 ```
 
 :::

apps/docs/src/packages/vitepress-theme.md

@@ -33,15 +33,15 @@ The theme includes the following features:
 ::: code-group
 
 ```sh [pnpm]
-pnpm add -D @sit-onyx/vitepress-theme
+pnpm add -D @sit-onyx/vitepress-theme@alpha
 ```
 
 ```sh [npm]
-npm install -D @sit-onyx/vitepress-theme
+npm install -D @sit-onyx/vitepress-theme@alpha
 ```
 
 ```sh [yarn]
-yarn install -D @sit-onyx/vitepress-theme
+yarn install -D @sit-onyx/vitepress-theme@alpha
 ```
 
 :::