Configure clangd for ESP-IDF development

Enable PlatformIO compilation database generation and configure
toolchain discovery for Clang-based editors.

.clangd

@@ -0,0 +1,10 @@
+CompileFlags:
+  Add:
+    - -isystem
+    - /home/mscholz/.platformio/packages/toolchain-xtensa-esp-elf/xtensa-esp-elf/include
+  Remove:
+    - -mlongcalls
+    - -mdisable-hardware-atomics
+    - -fstrict-volatile-bitfields
+    - -fno-tree-switch-conversion
+    - -fno-shrink-wrap

.zed/settings.json

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+// Folder-specific settings
+//
+// For a full list of overridable settings, and general information on folder-specific settings,
+// see the documentation: https://zed.dev/docs/configuring-zed#settings-files
+{
+  "lsp": {
+    "clangd": {
+      "binary": {
+        "path": "/usr/bin/clangd",
+        "arguments": [
+          "--background-index",
+          "--query-driver=/home/mscholz/.platformio/packages/**/bin/*"
+        ]
+      }
+    }
+  }
+}

extra_script.py

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+Import("env")
+
+env.Replace(COMPILATIONDB_INCLUDE_TOOLCHAIN=True)