Add plugin spellcheck docs (#60512)

docs/sources/developers/plugins/plugin-spellcheck.md

@@ -0,0 +1,67 @@
+# Configuring plugin spellcheck
+
+> ℹ️ This process is applicable only for grafana maintained plugins and only if the plugins are activated in drone.grafana.net for CI process.
+
+## What it is and why it is required
+
+The spellcheck CI step performs basic spellcheck against the plugin code and documentation.\
+It helps us to avoid showing things like this to our customers:
+
+![image](https://user-images.githubusercontent.com/1436174/208397307-4270cb57-b538-4c68-8b0f-67ab5d3b8dad.png)
+
+At the moment spellcheck is mandatory for all internal plugins.
+
+Under the hood, the pipeline uses [cspell npm package](https://www.npmjs.com/package/cspell) to perform the spellcheck.
+
+## Steps to configure spellcheck
+
+If you ended up here following the link from the failing CI then most probably you don't have spellcheck configured for your plugin. Follow the below steps to set it up.
+
+1. Install cspell package to your plugin's repo:
+
+```bash
+yarn add -D cspell@6.13.3
+```
+
+3. Add `spellcheck` command to the `scripts` section in `package.json` of your plugin:
+
+```
+"spellcheck": "cspell -c cspell.config.json \"**/*.{ts,tsx,js,go,md,mdx,yml,yaml,json,scss,css}\""
+```
+
+3. Create a `cspell.config.json` file in the repo root folder and add a basic config there:
+
+```json
+{
+  "ignorePaths": [
+    "coverage/**",
+    "cypress/**",
+    "dist/**",
+    "go.sum",
+    "mage_output_file.go",
+    "node_modules/**",
+    "provisioning/**/*.yaml",
+    "src/dashboards/*.json",
+    "**/testdata/**/*.json",
+    "**/testdata/**/*.jsonc",
+    "vendor/**",
+    "cspell.config.json",
+    "package.json",
+    "yarn.lock",
+    "docker-compose*.yaml",
+    "docker-compose*.yml"
+  ],
+  "ignoreRegExpList": [
+    // ignore multiline imports
+    "import\\s*\\((.|[\r\n])*?\\)",
+    // ignore single line imports
+    "import\\s*.*\".*?\""
+  ],
+  "words": ["grafana", "datasource", "datasources"]
+}
+```
+
+4. Run `yarn spellcheck` to see if there are any misspellings
+5. If errors found, either fix them or add to `ignorePaths` or `words` section of the `cspell.config.json` created earlier
+
+Sample PR to add spellcheck to your repo: https://github.com/grafana/athena-datasource/pull/185/files