Fix typos (#66)

This pull request addresses multiple minor documentation and code
comment fixes to correct typos and improve clarity. These changes do not
introduce functional modifications but enhance readability and
professionalism.

### Documentation Fixes:

* Corrected a typo in the "Security Considerations" section header in
`design/design.md`. ("Securty" → "Security")
* Fixed spelling errors in the "Governance and Community" section of
`design/design.md`. ("accomodating" → "accommodating")
* Updated the "Proposals" section in `design/design.md` to fix a typo.
("accomodate" → "accommodate")

### Code Comment Fixes:

* Corrected a typo in a comment in `mcp/logging.go`. ("LoggingMesssage"
→ "LoggingMessage")
* Fixed a typo in a comment in `mcp/streamable.go`. ("priviledged" →
"privileged")

<!-- Provide a brief summary of your changes -->

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->

This PR is for fixing some typos in the repo

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
by code diff

## Breaking Changes
<!-- Will users need to update their code or configurations? -->
N/A

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

mcp/streamable.go

@@ -254,7 +254,7 @@ func (s *StreamableServerTransport) Connect(context.Context) (Connection, error)
 //
 // Currently, this is implemented in [ServerSession.handle]. This is not ideal,
 // because it means that a user of the MCP package couldn't implement the
-// streamable transport, as they'd lack this priviledged access.
+// streamable transport, as they'd lack this privileged access.
 //
 // If we ever wanted to expose this mechanism, we have a few options:
 //  1. Make ServerSession an interface, and provide an implementation of