Add custom annotation to the map.

[toshanmugaraj]

Encrypt the annotations and store in the room state.
Use the pinned message as the password to encrypt and decrypt.
Delete annotation in the map.
Choose annotation color and description while marking.

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• [x ] Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[florianduros]

Hi, first of all thanks for the contribution!

According to the location sharing spec, we don't support custom annotation.We mustn't use pinned message to store this kind of data.

Also, you should read the code style guide before contributing.

[toshanmugaraj]

@florianduros I will start drafting the MSC to allow annotations inside map. Thank you for the feedback.