Add local_todo integration documentation

[allenporter]

Proposed change

Add local_todo integration documentation.

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • I've opened up a PR to add logo's and icons in Brands repository.
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase: Add a Local To-do component core#102627
• Link to parent pull request in the Brands repository: Add brand icon for local_todo component brands#4812
• This PR fixes or closes issue: fixes #

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.

[allenporter]

I could use some assistance understanding the check failure:

8:43:48 PM: build-image version: 0c5695ad82eb9b0111196b4ab87e76fc88dfb543 (focal)
8:43:48 PM: buildbot version: 44bdaa9bbaa9912838fe50ed0826ccd09db9f453
8:43:49 PM: Fetching cached dependencies
8:43:49 PM: Starting to download cache of 1010.4MB
8:44:02 PM: Finished downloading cache in 13.69s
8:44:02 PM: Starting to extract cache
8:44:06 PM: Failed during stage "preparing repo": git ref pull/29496/head does not exist
8:44:06 PM: Finished extracting cache in 3.766s
8:44:06 PM: Finished fetching cache in 17.558s
8:44:06 PM: Starting to prepare the repo for build
8:44:06 PM: git ref pull/29496/head does not exist or you do not have permission
8:44:06 PM: Failing build: Failed to prepare repo

[c0ffeeca7]

LGTM, @allenporter 👍