feat: add header component and update blog layout

- Introduced a new Header component for site navigation.
- Integrated Header into BaseLayout for consistent site structure.
- Updated blog post layout to include the post title in a dedicated section.
- Minor update to README for license clarity.

src/components/Header.astro

@@ -0,0 +1,22 @@
+<style lang="scss">
+	@import "../scss/_variables.scss";
+
+	header {
+		padding-bottom: 1rem;
+		text-align: right;
+	}
+
+	a {
+		text-decoration: none;
+		margin-right: 1.5rem;
+
+		&:last-child {
+			margin-right: 0;
+		}
+	}
+</style>
+
+<header>
+	<a href="/">Home</a>
+	<a href="/blog">Blog</a>
+</header>