Update documentation

[kevinwcyu]

• [x] CONTRIBUTING: Instruction for building backend is unclear. “build:backend” is listed as the build command, but should be “mage”
• [x] CONTRIBUTING: Update team name here https://github.com/grafana/timestream-datasource/blob/main/CONTRIBUTING.md#re-generating-json-api-response where it says “ping the @grafana/aws-plugins team”
• [x] CONTRIBUTING: https://github.com/grafana/timestream-datasource/blob/main/CONTRIBUTING.md#pre-requisites link to release.yaml is a 404
• [x] README: https://github.com/grafana/timestream-datasource/blob/main/src/README.md#query-editor image link to “query-editor” is broken
• [x] README: https://github.com/grafana/timestream-datasource/blob/main/src/README.md#alerting link to “Alerting documentation” is a 404
• [x] README: doesn’t have documentation for provisioning a data source. See the Athena data source README for an example of what to include

[nmarrs]

Re: link to release.yaml being broken it seems that at time of implementation there was no release.yaml file (and there is still no file) so I think it might of just been copying from another plugin that had this setup - I think updating it to match other plugins (like Athena) makes sense 👍