Ecosystem revamp: add missing tools & projects, provide a better structure

[novusnota]

Ecosystem→Tools:

• Nujan Web-based IDE — at least a reference to it would be nice
• Blueprint — common development environment for TON Blockchain to write, test, and deploy smart contracts.
• Tact-by-Example — somewhat referenced in the docs, but doesn't have a dedicated page in the Ecosystem yet

Grammars (highlighting & more):

• 🌳 Tree-sitter grammar for the ⚡ Tact contract programming language
• TextMate grammar — can be re-used for Shiki highlighting, as done in tact-docs.
• highlight.js-based grammar for Tact — syntax highlighting
• Prism.js grammar for Tact — syntax highlighting, added to ton-docs

Editors & IDEs:

• Vim 8+ and Neovim plugin for Tact — description + complete configs for beginners

VS Code extension and JetBrains plugin may be moved into a standalone sub-section called Editors & IDEs or something similar. Alternatively, the overview page of Ecosystem→Tools may be changed to provide a searchable structure, similar to tact-lang/awesome-tact.

This will partially resolve #47, except for the Helix editor, where highlighting support & basic configuration is already merged into their master, but I'd like to introduce LSP support + fine-tune queries and related to version 1.3.0, once it releases.

[anton-trunov]

We should also flatten the structure of /ecosystem, it takes to many clicks/taps to get to interesting places