[Logs Explorer] Add generic commands to Readme (elastic#171208)

## Summary

PR adds the list of regular commands we use in the project

x-pack/plugins/observability_log_explorer/README.md

@@ -1,3 +1,71 @@
 # Observability Log Explorer
 
 This plugin provides an app based on the `LogExplorer` component from the `log_explorer` plugin, but adds observability-specific affordances.
+
+## Testing
+
+### Stateful
+
+#### FTR Server
+```
+yarn test:ftr:server --config ./x-pack/test/functional/apps/observability_log_explorer/config.ts
+```
+
+#### FTR Runner
+```
+yarn test:ftr:runner --config ./x-pack/test/functional/apps/observability_log_explorer/config.ts --include ./x-pack/test/functional/apps/observability_log_explorer/index.ts
+```
+
+#### Running Individual Tests
+```
+yarn test:ftr:runner --config ./x-pack/test/functional/apps/observability_log_explorer/config.ts --include ./x-pack/test/functional/apps/observability_log_explorer/$1
+```
+
+### Serverless
+
+#### Server
+```
+yarn test:ftr:server --config ./x-pack/test_serverless/functional/test_suites/observability/config.ts
+```
+
+#### Runner
+```
+yarn test:ftr:runner --config ./x-pack/test_serverless/functional/test_suites/observability/config.ts --include ./x-pack/test_serverless/functional/test_suites/observability/observability_log_explorer/index.ts
+```
+#### Running Individual Tests
+```
+yarn test:ftr:runner --config ./x-pack/test_serverless/functional/test_suites/observability/config.ts --include ./x-pack/test_serverless/functional/test_suites/observability/observability_log_explorer/$1
+```
+
+## Checktypes
+
+#### Log Explorer
+```
+node scripts/type_check.js --project x-pack/plugins/log_explorer/tsconfig.json
+```
+#### Observability Log Explorer
+```
+node scripts/type_check.js --project x-pack/plugins/observability_log_explorer/tsconfig.json
+```
+
+### Generating Data using Synthtrace
+
+#### Logs Data only
+```
+node scripts/synthtrace simple_logs.ts --clean [--live]
+```
+
+#### Logs and Metrics Data
+```
+node scripts/synthtrace logs_and_metrics.ts --clean [--live]
+```
+
+### General Issues
+
+#### Kibana CI broken due to `kbn/optimiser` issue ?
+
+The limit is done to protect us in case we add some dependency that heavily impacts the bundle size, so this is not to be intended as a fix, but as a conscious update after double-checking the bundle size increase and see if it can be reduced
+
+```
+node scripts/build_kibana_platform_plugins --focus logExplorer --update-limits
+```