feat: implement experimental Flatpak support

Won't hurt, noone used this app yet.

.gitignore

@@ -63,3 +63,7 @@ test/test_runner
 # Added by cargo
 
 /target
+
+# Flatpak
+.flatpak-builder
+distro/flatpak/build

distro/flatpak/io.fortressia.Echidna.yml

@@ -0,0 +1,63 @@
+app-id: io.fortressia.Echidna
+runtime: org.gnome.Platform
+runtime-version: '41'
+sdk: org.gnome.Sdk
+sdk-extensions:
+ - org.freedesktop.Sdk.Extension.rust-stable
+command: echidna
+
+finish-args:
+  # Wayland access
+  - --socket=wayland
+  # X11 + XShm access
+  - --share=ipc
+  - --socket=x11
+  - --socket=fallback-x11
+  # Render with OpenGL
+  - --device=dri
+  # Network access (uncomment this when extension support have came)
+  # - --share=network
+cleanup: 
+  - '/include':
+modules: 
+  # Install libvte-gtk4 and libsourceview5 as they are not available in the GNOME runtime yet.
+  # - name: libvte
+  #  buildsystem: meson
+  #  config-opts: 
+  #    - "-Db_lto=false" 
+  #    - "-Dgtk3=false" 
+  #    - "-Dgtk4=true"
+  #  sources: 
+  #    - type: git
+  #      url: https://gitlab.gnome.org/GNOME/vte.git
+  #      tag: 0.66.2 
+  # 
+  # Uncomment this when terminal support is implemented
+  - name: libsourceview
+    buildsystem: meson
+    sources: 
+      - type: git
+        url: https://gitlab.gnome.org/GNOME/gtksourceview.git
+        tag: 5.3.0
+  - name: echidna
+    buildsystem: simple
+    build-commands: 
+      - source /usr/lib/sdk/rust-stable/enable.sh && cargo build --release
+      - install -D target/release/echidna /app/bin/echidna
+    build-options: 
+      build-args: 
+       - --share=network
+    sources: 
+      - type: git
+        # Use GitHub to avoid stressing Ariadne's infra.
+     #   url: https://github.com/EchidnaHQ/Echidna/
+        branch: feat/flatpak
+        path: ../../
+  - name: echidna-assets
+    buildsystem: simple
+    build-commands:
+          - install -d /app/share/applications
+          - install -D io.fortressia.Echidna.desktop /app/share/applications/ 
+    sources: 
+      - type: file
+        path: ../io.fortressia.Echidna.desktop

distro/io.fortressia.Echidna.desktop

@@ -0,0 +1,5 @@
+[Desktop Entry]
+Name=Echidna Code Editor
+Exec=echidna
+Type=Application
+Comment=A tolerable drop-in replacement for VSCode

src/main.rs

@@ -9,7 +9,7 @@ use components::app;
 use gtk::prelude::ApplicationExtManual;
 
 fn main() {
-    let app = EchidnaEditor::new("land.echidna.editor");
+    let app = EchidnaEditor::new("io.fortressia.Echidna");
 
     std::process::exit(app.run());
 }