enable markdown linter

[p0mvn]

Context

nit: we should have a markdown liner enabled

* [#1203](https://github.com/osmosis-labs/osmosis/pull/1203) cleanup Makefile and ci workflows

Originally posted by @alexanderbez in #1203 (comment)

Acceptance Criteria

• markdown linter is enabled and runs on all READMEs

[alexanderbez]

For reference, see what I did for Umee:

• Config: https://github.com/umee-network/umee/blob/main/.markdownlint.yml (we can add other rules to disable if we want)
• GH action job: https://github.com/umee-network/umee/blob/main/.github/workflows/lint.yml#L27-L43

[ValarDragon]

Here was the old issue I had lol: #88

If people want to retry it, I'm happy to do so. But its the sort of thing I don't think we should feel too attached to / isn't really that helpful.

I think the only ones I found helpful before were links. I found the newlines after header, and line length ones really cumbersome to fight against personally.

[alexanderbez]

The linter will help us have consistency in our markdown, which IMO, is one of the most important things in any codebase, both docs & code wise.

[p0mvn]

Drafted out a PR with this in #1317 to see how this works

Tried running the linter and there were hundreds, maybe thousands of issues. Unfortunately, the linter doesn't auto-fix them all. After auto-fix, it still seems like a few hours worth of work to fix them all manually.

One thing I also noted is that it would require further customization. For example, it complains about having headings with the same name in CHANGELOG

What is the consensus on this? Should I keep working? I would like to make sure that the team wants this before I spend time

Personally, I'm in support of encouraging consistency across the codebase but not sure if it's worth the time effort

[ValarDragon]

The only markdown lints I've found useful in the past limiting line lengths to 120 characters, and reminders for correct link syntax. I've otherwise found every other one counter-helpful.

Taking unnecesasrry time review/iteration time for things like newline after heading, only using - for lists, and not *, etc. Things that at least to me feel arbitrary. The justification for both of those as far as I'm aware is support with legacy markdown renderers, which I haven't observed these issues with.

I'm happy to adapt if other people want to use it, I'm generally not enthused about them though