feat(lang): add solidity language support (#4742)

## Description

### Summary

This PR adds comprehensive support for Solidity development in Neovim
using LazyVim. The following updates were made to streamline Solidity
development:
### Changes

1. **Solidity File Type Detection**
- Configured LazyVim to recognize Solidity projects by detecting
`foundry.toml`, `hardhat.config.js`, and `hardhat.config.ts` files.
2. **Treesitter Support for Solidity**
- Added `solidity` to the list of languages ensured by
`nvim-treesitter`, providing syntax highlighting and better code
structure understanding.
3. **Language Server Protocol (LSP) Setup**
- Configured `nvim-lspconfig` to support `solidity_ls` as the LSP for
Solidity files.
- Set up `root_dir` detection based on project files or a `.git`
directory to enable proper LSP functioning in Solidity projects.
4. **Solidity Formatter**
- Integrated `forge_fmt` as a formatter for Solidity files using
`conform.nvim`, which utilizes `forge fmt` to format code.
    
### Why use `forge fmt` instead of Prettier?

- **Prettier's Solidity support requires extra plugins**: Prettier does
not have native Solidity support and depends on
`prettier-plugin-solidity`. Even with
`vim.g.lazyvim_prettier_needs_config = false`, formatting won't work
unless a `.prettierrc` file is configured, creating unnecessary
complexity.
- **`forge fmt` is the native tool for Solidity development**: `Forge`
is a widely used tool within the Solidity ecosystem, especially when
working with Foundry. It provides built-in formatting with no extra
dependencies, making it simpler and more efficient to integrate.
- **Hardhat uses `prettier-plugin-solidity`**: For users of Hardhat,
`prettier-plugin-solidity` is required for code formatting. However, the
integration with Prettier might add complexity, while `forge fmt`
simplifies the process.
- **Future customization**: We may allow users to choose between
`prettier-plugin-solidity` and `forge fmt` for formatting in the future,
depending on their preferred tools.
    
  
### Testing

- Confirmed that Solidity files are detected and syntax-highlighted by
Treesitter.
- Verified LSP functionality for Solidity, including code navigation and
error detection.
- Tested `forge_fmt` for automatic code formatting on Solidity files.
### Motivation

These changes provide a smoother and more robust Solidity development
experience in Lazyvim, including syntax highlighting, code navigation,
and automatic formatting.

## Related Issue(s)
https://github.com/LazyVim/LazyVim/issues/1901

## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

---------

Co-authored-by: Folke Lemaitre <folke.lemaitre@gmail.com>

lua/lazyvim/plugins/extras/lang/solidity.lua

@@ -0,0 +1,42 @@
+return {
+  recommended = function()
+    return LazyVim.extras.wants({
+      ft = "solidity",
+      root = {
+        "foundry.toml",
+        "hardhat.config.js",
+        "hardhat.config.ts",
+      },
+    })
+  end,
+  -- Add Solidity & related to treesitter
+  {
+    "nvim-treesitter/nvim-treesitter",
+    opts = { ensure_installed = { "solidity" } },
+  },
+
+  -- Correctly setup lspconfig for Solidity
+  {
+    "neovim/nvim-lspconfig",
+    opts = {
+      servers = {
+        solidity_ls = {},
+      },
+    },
+  },
+  -- Formatter for Solidity
+  {
+    "conform.nvim",
+    opts = function(_, opts)
+      opts.formatters_by_ft = opts.formatters_by_ft or {}
+      opts.formatters_by_ft.solidity = { "forge_fmt" }
+
+      opts.formatters = {
+        forge_fmt = {
+          command = "forge",
+          args = { "fmt" },
+        },
+      }
+    end,
+  },
+}