nvim: Restructure lua dir

Moved plugins into individual component module files which are
automatically required by lazy.nvim. Should make everything a tiny bit
more modular, or at least prepare the way for true modularity if I ever
have the time on my hands to ensure everything works with missing
modules.

Moved core settings into their own directory (`core`), and created a
`personal` folder which contains functions/plugins I wrote that do not
necessarily have to be their own imported plugin yet.

Finally, extended the utility functions a little, so we can detect if a
plugin exists and change e.g. key maps based on that (once again,
extending modularity a little more). Some simple attempts have been made
at that in the `mappings.lua` file, though it is nowhere near extensive
yet - most keymaps are still set regardless of plugin availability.

However, with this slimmer base to work off of, I feel more confident in
changing future things about this setup a little more ad-hoc without
having as many ripple repercussions as before.

nvim/.config/nvim/lua/plugins/ide.lua

@@ -0,0 +1,73 @@
+return {
+	-- vista-like outline view for code
+	{ "simrat39/symbols-outline.nvim", config = true, cmd = "SymbolsOutline" },
+	-- show a signature whenever editing a function or similar
+	{ "ray-x/lsp_signature.nvim", config = true, event = "VeryLazy" },
+	{
+		"junnplus/lsp-setup.nvim",
+		dependencies = {
+			"neovim/nvim-lspconfig",
+			{
+				"williamboman/mason.nvim",
+				cmd = {
+					"Mason",
+					"MasonInstall",
+					"MasonUninstall",
+					"MasonUninstallAll",
+					"MasonLog",
+					"MasonUpdate",
+				},
+				build = ":MasonUpdate",
+			},
+			{
+				"williamboman/mason-lspconfig.nvim",
+				cmd = { "LspInstall", "LspUninstall" },
+			},
+			{
+				"jose-elias-alvarez/null-ls.nvim",
+				dependencies = {
+					"nvim-lua/plenary.nvim",
+					"jay-babu/mason-null-ls.nvim",
+				},
+				event = "VeryLazy",
+			},
+		},
+		event = "BufReadPost",
+		config = function()
+			require("plugins.config.lsp")
+		end,
+	},
+	{
+		"hrsh7th/nvim-cmp",
+		branch = "main",
+		dependencies = {
+			"andersevenrud/cmp-tmux",
+			"cbarrete/completion-vcard",
+			"f3fora/cmp-spell",
+			"hrsh7th/cmp-nvim-lsp",
+			"hrsh7th/cmp-path",
+			"hrsh7th/cmp-buffer",
+			"hrsh7th/cmp-calc",
+			"hrsh7th/cmp-cmdline",
+			"hrsh7th/cmp-nvim-lua",
+			"dmitmel/cmp-digraphs",
+			"jc-doyle/cmp-pandoc-references",
+			"kdheepak/cmp-latex-symbols",
+			"lukas-reineke/cmp-rg",
+			"crispgm/cmp-beancount",
+			"ray-x/cmp-treesitter",
+			"saadparwaiz1/cmp_luasnip",
+			{
+				"L3MON4D3/LuaSnip",
+				dependencies = { "rafamadriz/friendly-snippets" },
+			},
+		},
+		config = function()
+			require("plugins.config.cmp")
+		end,
+		event = { "InsertEnter", "CmdlineEnter", "VeryLazy" },
+	},
+	-- loading animations for some LSP
+	{ "j-hui/fidget.nvim", config = true, tag = "legacy", event = "VeryLazy" },
+	-- a pretend-lsp for formatters and linters
+}