Scripts doc rework

[basteks]

Massive rework:

General

• New plugin mkdocs-include-markdown-plugin allowing to insert a file section in different places (one single place to modify)
• More links to SeaTable help manual for additional information
• Simplified icon use
• Restructured functions lists with consistency in mind

Introduction section

• Restructured information (with a new Coding for beginners page)

Scripting in SeaTable section

Objects & Methods

• [JS/Python] Restructured/simplified introduction
• [JS/Python] Added global structure presentation for main elements (Tables, Views, Columns, Rows, Links)
• Added few
• [Python] merged Notifications + Websockets (and added webhooks) in a single Communication utility functions page

Examples

• [JS/Python] Updated examples (correcting JS and Python, adding JS examples equivalents to Python)

Common questions

• [JS/Python] Added few new questions

SQL

• Restructured introduction based on the query syntax (statements then clauses then operators)