Mdx support and several changes (#5)

# Mdx files supported

- Mdx plugin was added to Astro. The project can render `mdx` and `md`
files.
- Latest post is displayed on `index.astro` as main page.
- Content collection API is used to query posts pages. `env.d.ts` and
`tsconfig.json` were modified.
- A template page was created to host markdown contents
`[...slug].astro`.

# Other changes

- Poppins font was added to project.
- `global.css` was modified to include new font a some UI changes.
- Aliases were added to reduce import path in pages, components and
layouts.
- Navigation was added to list all posts, it is on `Footer` component
- Post's title redirect to home.

# Fixes
- #1
- #2
- #3
- #4

astro.config.mjs

@@ -1,4 +1,9 @@
 import { defineConfig } from 'astro/config';
 
+import mdx from "@astrojs/mdx";
+
 // https://astro.build/config
-export default defineConfig({});
+export default defineConfig({
+  integrations: [mdx()],
+  output: "hybrid"
+});