Initial markdown support

Markdown doesnt have a language server, so do this manually
Closes #43

lua/symbols-outline/config.lua

@@ -65,9 +65,7 @@ function M.get_position_navigation_direction()
     end
 end
 
-function M.get_width_percentage()
-    return M.options.width / 100
-end
+function M.get_width_percentage() return M.options.width / 100 end
 
 function M.get_split_command()
     if M.options.position == 'left' then
@@ -90,6 +88,7 @@ end
 
 function M.is_client_blacklisted(client_id)
     local client = vim.lsp.get_client_by_id(client_id)
+    if not client then return false end
     return has_value(M.options.lsp_blacklist, client.name)
 end
 

lua/symbols-outline/markdown.lua

@@ -0,0 +1,37 @@
+local M = {}
+
+---Parses markdown files and returns a table of SymbolInformation[] which is
+-- used by the plugin to show the outline.
+-- We do this because markdown does not have a LSP.
+-- Note that the headings won't have any heirarchy (as of now).
+---@return table
+function M.handle_markdown()
+    local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
+    local results = {}
+
+    for line, value in ipairs(lines) do
+        if string.find(value, "^#+") then
+            if #results > 0 then
+               results[#results].selectionRange["end"].line = line - 1
+               results[#results].range["end"].line = line - 1
+            end
+
+            table.insert(results, {
+                kind = 13,
+                name = value,
+                selectionRange = {
+                    start = {character = 1, line = line - 1},
+                    ["end"] = {character = 1, line = line - 1}
+                },
+                range = {
+                    start = {character = 1, line = line - 1},
+                    ["end"] = {character = 1, line = line - 1}
+                }
+            })
+        end
+    end
+
+    return {[1000000]={result=results}}
+end
+
+return M

lua/symbols-outline/utils/lsp_utils.lua

@@ -7,4 +7,8 @@ function M.is_buf_attached_to_lsp(bufnr)
     return clients ~= nil and #clients > 0
 end
 
+function M.is_buf_markdown(bufnr)
+   return vim.api.nvim_buf_get_option(bufnr, 'ft') == 'markdown'
+end
+
 return M