Link for "New Post" is added in Getting Started guide [ci skip]

- Earlier(line number 862) it is said to add <%= link_to 'New post', new_post_path %> on posts index page before table tag. But when posts index page html is shown, "New Post" link is missing.
So aaded "New Post" link in this commit
[ci skip] used new syntax for scopes
Merge pull request #13070 from kuldeepaggarwal/documentation-updation

[ci skip] used new syntax for scopes
[ci skip]removed obsolete information about `options` parameter in create method
Merge pull request #13071 from kuldeepaggarwal/documentation-updation

[ci skip]removed obsolete information about `options` parameter in create method
Merge pull request #13069 from chancancode/json_gem_version

Requires JSON gem version 1.7.7 or above as it contains an important security fix.
Merge pull request #13068 from chancancode/drop_yajl_from_gemfile

Dropped yajl from Gemfile
Merge pull request #13067 from sagarjunnarkar/getting_started

Link for "New Post" is added in Getting Started guide [ci skip]
unnecessary checking of `size` with `second regex` if matched with first one
Merge pull request #13072 from kuldeepaggarwal/unwanted-code

unnecessary checking of `size` with `second regex` if matched with former regex
Merge branch 'deprecate_numeric_since_ago' of https://github.com/chancancode/rails

Conflicts:
	activesupport/CHANGELOG.md
Added failing test for json_escape striping quotation marks

Expanded test coverage for html_escape and json_escape
Fixed a long-standing bug in `json_escape` that strips quotation marks
Use lower case letters in unicodes sequences to match the new encoder's output