Don't search for tags within code blocks

[jayemar]

If a note has a code block that includes words preceded by octothorpes, they're currently recognized as tags by obsidian.el, but they shouldn't be. For example, in the following snippet of arduino code, ifndef, define, and endif will all be incorrectly recognized as tags.

#ifndef LED_BUILTIN
#define LED_BUILTIN 13
#endif

pinMode(LED_BUILTIN, OUTPUT);

Obsidian does not recognize these as tags and so therefore neither should we.