Click file paths to open in editor, allow plugins to change styles and hover of viewport (#4802)

* initial implementation

* implement hover

* add styles and foreground/background emphases, fix upsert hover collisions

* initial implementation of link plugin

* suppress highlighting + clicks on unfocused and mouse mode panes

* also make italic

* fix env var and ~ expansions

* fix regex issues and add defensive validations

* fix tests and add plugin assets

* add tests

* refactor all the things

* add pr

xtask/src/main.rs

@@ -82,6 +82,10 @@ fn workspace_members() -> &'static Vec<WorkspaceMember> {
                 crate_name: "default-plugins/layout-manager",
                 build: true,
             },
+            WorkspaceMember {
+                crate_name: "default-plugins/link",
+                build: true,
+            },
             WorkspaceMember {
                 crate_name: "zellij-utils",
                 build: false,