Strip hashes from markdown headers

[FireController1847]

It seems more reasonable to strip the hashes and use the inherent nature of the symbol's children to determine the associated levels for each header. This will tie into a PR in VS Code, in addition to microsoft/vscode-codicons#442, which adds icons to further distinguish between header levels.

This is how I fetched the level heading in an extension I was designing using Lua. It's very possible and, imo, more practical since hashes are markdown-specific anyway:

---@param symbols LuaSymbol[]
---@return StructureNode[]
function GetDocumentStructure(symbols, level)
    local structure = {}
    if not level then
        level = 1
    end
    for i = 1, #symbols do
        local symbol = symbols[i]
        local line = 0
        if symbol.selectionRange and symbol.selectionRange.start then
            line = symbol.selectionRange.start.line
        elseif symbol.range and symbol.range.start then
            line = symbol.range.start.line
        end
        local name = symbol.name:gsub("#", ""):gsub("^%s+", ""):gsub("%s+$", "")
        local node = MakeNode(name, "h" .. level, line)
        if (symbol.children) then
            node.children = GetDocumentStructure(symbol.children, level + 1)
        end
        table.insert(structure, node)
    end
    return structure
end