feat: register/update prompt

[LintaoAmons]

Description

With this PR, you can use a new method to register a new action or update an existing action
The register call can happen from anywhere and anytime, it doesn't require you restart the neovim to take effect.

try with this snippet, put it anywhere and source it, then you can find the registered action in the action palette

require("codecompanion.config").register_prompt("test register_prompt with references", {
  -- TODO: define a chat name to make it easier when trying to find it with `OpenChat`
  strategy = "chat",
  description = "Add some references",
  opts = {
    index = 11,
    is_default = true,
    is_slash_cmd = false,
    short_name = "ref",
    auto_submit = false,
  },
  -- These will appear at the top of the chat buffer
  references = {
    {
      type = "file",
      path = { -- This can be a string or a table of values
        "lua/codecompanion/health.lua",
        "lua/codecompanion/http.lua",
      },
    },
    {
      type = "file",
      path = "lua/codecompanion/schema.lua",
    },
    {
      type = "symbols",
      path = "lua/codecompanion/strategies/chat/init.lua",
    },
    {
      type = "url", -- This URL will even be cached for you!
      url = "https://raw.githubusercontent.com/olimorris/codecompanion.nvim/refs/heads/main/lua/codecompanion/commands.lua",
    },
  },
  prompts = {
    {
      role = "user",
      content = "I'll think of something clever to put here...",
      opts = {
        contains_code = true,
      },
    },
  },
})

Related Issue(s)

#649

Screenshots

Checklist

• I've read the CONTRIBUTING guidelines and have adhered to them in this PR
• I've updated the README
• I've ran the make docs command

[olimorris]

Amazing! Let me know when you're happy for me to review

[LintaoAmons]

LintaoAmons/bookmarks.nvim#71

Provide the context with the bookmarks in a list with my bookmarks.nvim plugin

[LintaoAmons]

I add this test file to help you review the functions,
if you want to merge it, we can remove it

[LintaoAmons]

@olimorris Please review~

[olimorris]

Awesome thanks for this. I will test this out today/tomorrow.