Add crates.nvim keymaps

lua/plugins/lsp/on_attach.lua

@@ -1,3 +1,17 @@
+-- From: https://github.com/Saecki/crates.nvim
+local function show_documentation()
+    local filetype = vim.bo.filetype
+    if vim.tbl_contains({ 'vim','help' }, filetype) then
+        vim.cmd('h '..vim.fn.expand('<cword>'))
+    elseif vim.tbl_contains({ 'man' }, filetype) then
+        vim.cmd('Man '..vim.fn.expand('<cword>'))
+    elseif vim.fn.expand('%:t') == 'Cargo.toml' and require('crates').popup_available() then
+        require('crates').show_popup()
+    else
+        vim.lsp.buf.hover()
+    end
+end
+
 -- Use an on_attach function to only map the following keys
 -- after the language server attaches to the current buffer
 -- thallada: NOTE: copied also in lsp/init.lua since I can't figure out how to import it here
@@ -9,7 +23,7 @@ local on_attach = function(_, bufnr)
   -- See `:help vim.lsp.*` for documentation on any of the below functions
   local bufopts = { noremap=true, silent=true, buffer=bufnr }
   vim.keymap.set('n', 'gD', vim.lsp.buf.declaration, bufopts)
-  vim.keymap.set('n', 'K', vim.lsp.buf.hover, bufopts)
+  vim.keymap.set('n', 'K', show_documentation, bufopts)
   vim.keymap.set('n', 'gi', vim.lsp.buf.implementation, bufopts)
   vim.keymap.set('n', '<M-k>', vim.lsp.buf.signature_help, bufopts)
   vim.keymap.set('n', '<leader>wa', vim.lsp.buf.add_workspace_folder, bufopts)