fix: hashtag matcher

[foolo]

What does this PR do?

• Detect hashtags with digits, for example #web3,
• Detect hashtags with underscore, for example #foo_bar
• Ignore hashtags with only digits and/or underscore, for example #123, #12_34, #_)

Before fix:

After fix:

Here is a live example post which contains #Web3 hashtag: https://lenster.xyz/posts/0x73a4-0x029e

Type of change

• Bug fix (non-breaking change which fixes an issue)

How should this be tested?

• Create and view a post with the text. #lens #web3 #foo_bar #123 #_ #12_34 #foo! #bar? #test. dfg
• Verify that only #lens, #web3, #foo_bar, #foo and #bar are detected as hashtags.

[vercel]

@foolo is attempting to deploy a commit to the Lenster Team on Vercel.

A member of the Team first needs to authorize it.

[foolo]

@bigint I'm not sure if it's OK to just open a PR like this, without creating an issue first. Is it fine?, or should there always be an issue first?

[bigint]

It's perfectly fine 😊

[foolo]

Great, good to know! :)