Add frontmatter, markdown, path, xml, rss, and web packages

Sync local packages into the registry repo and update index.json
and README.md to include all 9 packages.

packages/path/lib.lux

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+// path - File path utilities for Lux
+
+// Get the last component of a path (filename)
+// basename("/foo/bar/baz.txt") => "baz.txt"
+// basename("file.txt") => "file.txt"
+pub fn basename(path: String): String =
+    match String.lastIndexOf(path, "/") {
+    Some(idx) => String.substring(path, idx + 1, String.length(path)),
+    None => path,
+}
+
+// Get the directory portion of a path
+// dirname("/foo/bar/baz.txt") => "/foo/bar"
+// dirname("file.txt") => "."
+pub fn dirname(path: String): String =
+    match String.lastIndexOf(path, "/") {
+    Some(idx) => if idx == 0 then "/" else String.substring(path, 0, idx),
+    None => ".",
+}
+
+// Get the file extension (without the dot)
+// extension("file.txt") => Some("txt")
+// extension("file") => None
+// extension("file.tar.gz") => Some("gz")
+pub fn extension(path: String): Option<String> = {
+    let name = basename(path)
+    match String.lastIndexOf(name, ".") {
+    Some(idx) => if idx == 0 then None
+        else Some(String.substring(name, idx + 1, String.length(name))),
+    None => None,
+}
+}
+
+// Remove the file extension
+// stripExtension("file.txt") => "file"
+// stripExtension("file") => "file"
+// stripExtension("/foo/bar.txt") => "/foo/bar"
+pub fn stripExtension(path: String): String =
+    match String.lastIndexOf(path, ".") {
+    Some(dotIdx) => match String.lastIndexOf(path, "/") {
+        Some(slashIdx) => if dotIdx > slashIdx then String.substring(path, 0, dotIdx) else path,
+        None => String.substring(path, 0, dotIdx),
+    },
+    None => path,
+}
+
+// Join two path components with a separator
+// join("/foo", "bar") => "/foo/bar"
+// join("/foo/", "bar") => "/foo/bar"
+// join("", "bar") => "bar"
+pub fn join(a: String, b: String): String =
+    if a == "" then b
+    else if b == "" then a
+    else if String.endsWith(a, "/") then
+        if String.startsWith(b, "/") then a + String.substring(b, 1, String.length(b))
+        else a + b
+    else if String.startsWith(b, "/") then a + b
+    else a + "/" + b
+
+// Check if a path has a given extension
+// hasExtension("file.txt", "txt") => true
+// hasExtension("file.md", "txt") => false
+pub fn hasExtension(path: String, ext: String): Bool =
+    String.endsWith(path, "." + ext)
+
+// Replace the file extension
+// replaceExtension("file.txt", "md") => "file.md"
+// replaceExtension("file", "md") => "file.md"
+pub fn replaceExtension(path: String, newExt: String): String =
+    stripExtension(path) + "." + newExt
+
+// Get the filename without extension (stem)
+// stem("file.txt") => "file"
+// stem("/foo/bar.txt") => "bar"
+// stem("file") => "file"
+pub fn stem(path: String): String = {
+    let name = basename(path)
+    match String.lastIndexOf(name, ".") {
+    Some(idx) => if idx == 0 then name
+        else String.substring(name, 0, idx),
+    None => name,
+}
+}
+
+// Check if a path is absolute (starts with /)
+pub fn isAbsolute(path: String): Bool =
+    String.startsWith(path, "/")
+
+// Check if a path is relative (does not start with /)
+pub fn isRelative(path: String): Bool =
+    if path == "" then true
+    else if String.startsWith(path, "/") then false
+    else true