[docs] add CodingStyle + Coding guidelines, HOS kernel basics, 'Settings' and add external resources, add better docs for dtrace-tool.pl (#3964)

Signed-off-by: lizzie <lizzie@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3964
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

docs/README.md

@@ -2,21 +2,26 @@
 
 Are you just a casual user? Take a look at our [User Handbook](./user) then!
 
+If you want to register/signup as a contributor, take a gander at the [signup guide](./SIGNUP.md).
+
 This contains documentation created by developers. This contains build instructions, guidelines, instructions/layouts for [cool stuff we made](./CPMUtil), and more.
 
-- **[General Build Instructions](Build.md)**
-- **[CMake Options](Options.md)**
-- **[Cross Compiling](CrossCompile.md)**
-- **[Development Guidelines](Development.md)**
-- **[Dependencies](Deps.md)**
+- **[General Build Instructions](./Build.md)**
+- **[CMake Options](./Options.md)**
+- **[Cross Compiling](./CrossCompile.md)**
+- **[Development Guidelines](./Development.md)**
+- **[Dependencies](./Deps.md)**
 - **[Debug Guidelines](./Debug.md)**
 - **[CPM - CMake Package Manager](./CPMUtil)**
-- **[Platform-Specific Caveats](Caveats.md)**
+- **[Platform-Specific Caveats](./Caveats.md)**
 - **[The NVIDIA SM86 (Maxwell) GPU](./NvidiaGpu.md)**
-- **[Dynarmic](./dynarmic)**
 - **[Cross compilation](./CrossCompile.md)**
 - **[Driver Bugs](./DriverBugs.md)**
 - **[Building Older Commits](./build/OlderCommits.md)**
+- Subsystems:
+    - **[Dynarmic](./dynarmic/README.md)**
+    - **[HOS Kernel](./HosKernel.md)**
+    - **[Settings](./Settings.md)**
 
 ## Policies
 
@@ -25,3 +30,12 @@ Policies and information on development.
 - **[AI and LLM Usage](./policies/AI.md)**
 - **[Release Policy](./policies/Release.md)**
 - **[Coding guidelines](./policies/Coding.md)**
+- **[Coding Style guidelines](./policies/CodingStyle.md)**
+
+## Externals
+
+Other useful resources in general, take a quick read if you need.
+
+- **[SwitchBrew](https://switchbrew.org/wiki/Main_Page)**
+- **[IPS file format](https://zerosoft.zophar.net/ips.php)**
+- **[IPSwitch file format](https://github.com/3096/ipswitch)**