Added SLNX solution file

Added the new CSTNet.slnx solution file and updated the README to mention the deprecation of the .sln solution type in favor of .slnx. Also fixed minor formatting issues in the README.

CSTNet.slnx

@@ -0,0 +1,9 @@
+<Solution>
+  <Folder Name="/Solution Items/">
+    <File Path=".editorconfig" />
+    <File Path="doc/changelog.md" />
+    <File Path="README.md" />
+  </Folder>
+  <Project Path="CSTNet.Tests/CSTNet.Tests.csproj" />
+  <Project Path="CSTNet/CSTNet.csproj" />
+</Solution>

README.md

@@ -6,7 +6,7 @@ Caret-Separated Text (or CST) is a key-value pair format represented by digits o
 
 ## 🛠 Features
 
-- [x] Native support for Sims Online's `.cst `files.
+- [x] Native support for Sims Online's `.cst` files.
 - [x] UIText Support
 - [ ] Variable support
 
@@ -25,7 +25,6 @@ Caret-Separated Text (or CST) is a key-value pair format represented by digits o
 - [ ] Maintenance Mode (Dependency-only updates)
 - [ ] Archived (No active work planned)
 
-
 ## 🧰 Prerequisites
 
 Before you begin, ensure you have the latest versions of the following installed:
@@ -36,7 +35,9 @@ Before you begin, ensure you have the latest versions of the following installed
 
 - This all began as a "what if?" What if I could make my own? So, I did. First from a Jupyter notebook and then a full-fledged project that technically has a support cycle.
 - While this project is technically feature complete, it is not a full drop-in replacement as it lacks variable (`%[digit]`) parsing.
+- I'm deprecating the `.sln` solution type in favour of `.slnx` going forward. It'll be removed sometime in the future.
 
 ## 📄 License
 
 I license this project under BSD-3-Clause license — see the [LICENSE](LICENSE) file for full text.
+