FM 12 bulletin guidance for web-app users

[alimand]

User story

As a user who is not familiar with the FM 12 bulletin, he/she wants to see some guidances or tips on what information should he/she put in Raw FM 12 bulletin box so that he can publish related observation data in correct way based on his/her requirements on WIS2.

[david-i-berry]

Update docs to include information from: https://training.wis2box.wis.wmo.int/practical-sessions/converting-synop-data-to-bufr/

Also note that the form is for someone who already has a FM-12 SYNOP message and to not encode it by hand.

[tomkralidis]

2024-07-24:

• data should already be in FM-12 if using the FM-12 form
• add info link to wis2box-webapp on FM-12 proper? @david-i-berry to provide link for both webapp and docs

[tomkralidis]

Fixed in #746