feat: enhance build configuration with C++ standard support and variable substitution

- Added `cxx_standard` field to the build configuration for specifying C++ standards.
- Updated documentation to reflect new `cxx_standard` and variable substitution capabilities in `cflags`, `ldflags`, and `include`.
- Implemented logic to handle C++ standard flags in the build process.
- Modified object file naming to include source file extensions.
- Updated various builder modules to support new language parsing logic.
- Introduced issue and feature request templates for better community engagement.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,51 @@
+---
+name: Bug Report
+about: Something is broken or behaves unexpectedly
+title: "[bug] "
+labels: bug
+assignees: ''
+---
+
+## Description
+
+<!-- A clear and concise description of the bug -->
+
+## Steps to Reproduce
+
+1. 
+2. 
+3. 
+
+## Expected Behavior
+
+<!-- What should have happened -->
+
+## Actual Behavior
+
+<!-- What actually happened, include full error output -->
+
+```
+paste error output here
+```
+
+## Environment
+
+- **DCR version** (`dcr --version`): 
+- **OS**: 
+- **Compiler / toolchain** (`gcc --version` or `clang --version`): 
+
+## Minimal Reproducible Project
+
+<!-- If possible, share a minimal dcr.toml + source that reproduces the issue -->
+
+```toml
+# dcr.toml
+```
+
+```c
+// src/main.c
+```
+
+## Additional Context
+
+<!-- Anything else that might help -->