feat: add bootc support to Fedora atomic distros

* feat(bootc): add Bootc support + docs

Co-authored-by: Steve Lau <stevelauc@outlook.com>

* docs(bootc): specify that itll supercede rpm-ostree if enabled :p

---------

Co-authored-by: Steve Lau <stevelauc@outlook.com>

src/config.rs

@@ -358,6 +358,7 @@ pub struct Linux {
     redhat_distro_sync: Option<bool>,
     suse_dup: Option<bool>,
     rpm_ostree: Option<bool>,
+    bootc: Option<bool>,
 
     #[merge(strategy = crate::utils::merge_strategies::string_append_opt)]
     emerge_sync_flags: Option<String>,
@@ -1457,6 +1458,15 @@ impl Config {
             .unwrap_or(false)
     }
 
+    /// Use bootc in *when bootc is detected* (default: false)
+    pub fn bootc(&self) -> bool {
+        self.config_file
+            .linux
+            .as_ref()
+            .and_then(|linux| linux.bootc)
+            .unwrap_or(false)
+    }
+
     /// Determine if we should ignore failures for this step
     pub fn ignore_failure(&self, step: Step) -> bool {
         self.config_file